refactor(application): replace ISender dispatch with direct IRepository usage in email handlers

- FetchEmailsQuery, MarkEmailAsSeenCommand, PublishEmailCommand: resolve EmailAccount
  via IRepository<EmailAccount> instead of dispatching GetEmailAccountQuery through ISender
- Swap InvalidOperationException for BadRequestException when IMAP server is not configured
- Add ILogger to handlers; warn when multiple accounts match the lookup criteria
- EmailAccountsOptions.Accounts now typed as IEnumerable<EmailAccountModificationDto>
  instead of IEnumerable<EmailAccount> to decouple config from domain entity
- EmailMappingProfile: add EmailAccount <-> EmailAccountDto/EmailAccountModificationDto maps

src/core/DigitalData.MessagingService.Application/Common/Mappings/EmailMappingProfile.cs

@@ -2,6 +2,8 @@
 using AutoMapper;
 using DigitalData.MessagingService.Application.EmailSending.Commands;
 using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Domain.Entities;
+using DigitalData.MessagingService.Application.Common.Dto.EmailAccounts;
 
 namespace DigitalData.MessagingService.Application.Common.Mappings;
 
@@ -17,6 +19,10 @@ public class EmailMappingProfile : Profile
         CreateMap<PublishEmailCommand, EmailContext>()
             .ForMember(dest => dest.Sender, opt => opt.Ignore())
             .ForMember(dest => dest.Attachments, opt => opt.MapFrom(src => src.Attachments));
+
+        // EmailAccountDto -> EmailAccount
+        CreateMap<EmailAccount, EmailAccountDto>();
+        CreateMap<EmailAccountModificationDto, EmailAccount>();
     }
 }
 #endif

src/core/DigitalData.MessagingService.Application/Common/Options/EmailAccountsOptions.cs

@@ -1,4 +1,7 @@
 #if NET
+using DigitalData.MessagingService.Application.Common.Dto;
+using DigitalData.MessagingService.Application.Common.Dto.EmailAccounts;
+using DigitalData.MessagingService.Application.EmailAccounts.Commands;
 using DigitalData.MessagingService.Domain.Entities;
 
 namespace DigitalData.MessagingService.Application.Common.Options;
@@ -14,7 +17,7 @@ public class EmailAccountsOptions
     /// <summary>
     /// The list of configured email accounts.
     /// </summary>
-    public required IEnumerable<EmailAccount> Accounts { get; init; } = [];
+    public required IEnumerable<EmailAccountModificationDto> Accounts { get; init; } = [];
 
     /// <summary>
     /// How often the IMAP sync worker polls for new emails, in seconds.

src/core/DigitalData.MessagingService.Application/EmailReceiving/Commands/MarkEmailAsSeenCommand.cs

@@ -1,8 +1,11 @@
 #if NET
 using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
 using DigitalData.MessagingService.Application.EmailAccounts.Queries;
+using DigitalData.MessagingService.Domain.Entities;
 using DigitalData.MessagingService.Domain.Exceptions;
 using MediatR;
+using Microsoft.Extensions.Logging;
 
 namespace DigitalData.MessagingService.Application.EmailReceiving.Commands;
 
@@ -11,7 +14,7 @@ namespace DigitalData.MessagingService.Application.EmailReceiving.Commands;
 /// </summary>
 public record MarkEmailAsSeenCommand : IRequest
 {
-    public required GetSenderQuery Account { get; init; }
+    public required GetEmailAccountQuery Account { get; init; }
 
     /// <summary>
     /// UID of the message to mark as seen.
@@ -24,19 +27,20 @@ public record MarkEmailAsSeenCommand : IRequest
     public string Folder { get; init; } = "INBOX";
 }
 
-public class MarkEmailAsSeenCommandHandler(
-    ISender Sender,
-    IImapEmailService ImapService) : IRequestHandler<MarkEmailAsSeenCommand>
+public class MarkEmailAsSeenCommandHandler(IImapEmailService ImapService, ILogger<MarkEmailAsSeenCommandHandler> Logger, IRepository<EmailAccount> Repo) : IRequestHandler<MarkEmailAsSeenCommand>
 {
     public async Task Handle(MarkEmailAsSeenCommand request, CancellationToken cancellationToken)
     {
-        var account = await Sender.Send(request.Account, cancellationToken)
-            ?? throw new NotFoundException(
-                $"No email account found for the given criteria (Id: {request.Account.Id}, Username: {request.Account.Username}).");
+        var accounts = await Repo.FindAsync(request.Account.Id is int id ? x => x.Id == id : x => x.Username == request.Account.Username, cancellationToken: cancellationToken);
+
+        if (accounts.Count() > 1)
+            Logger.LogWarning("Multiple email accounts found for the given criteria ({Criteria}). Returning the first one.", request.Account.Id is not null ? $"Id: {request.Account.Id}" : $"Username: {request.Account.Username}");
+
+        var account = accounts.FirstOrDefault()
+            ?? throw new NotFoundException($"No email account found for the given criteria (Id: {request.Account.Id}, Username: {request.Account.Username}).");
 
         if (string.IsNullOrWhiteSpace(account.ImapServer))
-            throw new InvalidOperationException(
-                $"IMAP is not configured for account '{account.Username}' (Id: {account.Id}). Set ImapServer in EmailAccounts configuration.");
+            throw new BadRequestException($"IMAP is not configured for account '{account.Username}' (Id: {account.Id}). Set ImapServer in EmailAccounts configuration.");
 
         await ImapService.MarkAsSeenAsync(account, request.Uid, request.Folder, cancellationToken);
     }

src/core/DigitalData.MessagingService.Application/EmailReceiving/Queries/FetchEmailsQuery.cs

@@ -2,9 +2,12 @@
 using DigitalData.MessagingService.Application.Common.Dto;
 using DigitalData.MessagingService.Application.Common.Dto.MailSearch;
 using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
 using DigitalData.MessagingService.Application.EmailAccounts.Queries;
+using DigitalData.MessagingService.Domain.Entities;
 using DigitalData.MessagingService.Domain.Exceptions;
 using MediatR;
+using Microsoft.Extensions.Logging;
 
 namespace DigitalData.MessagingService.Application.EmailReceiving.Queries;
 
@@ -16,7 +19,7 @@ public record FetchEmailsQuery : IRequest<IEnumerable<ReceivedEmailDto>>
     /// <summary>
     /// Identifies the email account to use.
     /// </summary>
-    public required GetSenderQuery Account { get; init; }
+    public required GetEmailAccountQuery Account { get; init; }
 
     /// <summary>
     /// Mail query used to filter and limit the emails retrieved.
@@ -24,18 +27,20 @@ public record FetchEmailsQuery : IRequest<IEnumerable<ReceivedEmailDto>>
     public MailSearchFilter Mail { get; init; } = new();
 }
 
-public class FetchEmailsQueryHandler(
-    ISender Sender,
-    IImapEmailService ImapService) : IRequestHandler<FetchEmailsQuery, IEnumerable<ReceivedEmailDto>>
+public class FetchEmailsQueryHandler(IImapEmailService ImapService, ILogger<FetchEmailsQueryHandler> Logger, IRepository<EmailAccount> Repo) : IRequestHandler<FetchEmailsQuery, IEnumerable<ReceivedEmailDto>>
 {
     public async Task<IEnumerable<ReceivedEmailDto>> Handle(FetchEmailsQuery request, CancellationToken cancellationToken)
     {
-        var account = await Sender.Send(request.Account, cancellationToken)
-            ?? throw new NotFoundException(
-                $"No email account found for the given criteria (Id: {request.Account.Id}, Username: {request.Account.Username}).");
+        var accounts = await Repo.FindAsync(request.Account.Id is int id ? x => x.Id == id : x => x.Username == request.Account.Username, cancellationToken: cancellationToken);
+
+        if (accounts.Count() > 1)
+            Logger.LogWarning("Multiple email accounts found for the given criteria ({Criteria}). Returning the first one.", request.Account.Id is not null ? $"Id: {request.Account.Id}" : $"Username: {request.Account.Username}");
+
+        EmailAccount account = accounts.FirstOrDefault()
+            ?? throw new NotFoundException($"No email account found for the given criteria (Id: {request.Account.Id}, Username: {request.Account.Username}).");
 
         if (string.IsNullOrWhiteSpace(account.ImapServer))
-            throw new InvalidOperationException(
+            throw new BadRequestException(
                 $"IMAP is not configured for account '{account.Username}' (Id: {account.Id}). Set ImapServer in EmailAccounts configuration.");
 
         return await ImapService.FetchEmailsAsync(

src/core/DigitalData.MessagingService.Application/EmailSending/Commands/PublishEmailCommand.cs

@@ -1,11 +1,14 @@
 #if NET
 using AutoMapper;
-using DigitalData.MessagingService.Domain.Exceptions;
 using DigitalData.MessagingService.Application.Common.Dto;
-using MediatR;
-using System.Text.Json.Serialization;
 using DigitalData.MessagingService.Application.Common.Interfaces;
+using DigitalData.MessagingService.Application.Common.Interfaces.Repositories;
 using DigitalData.MessagingService.Application.EmailAccounts.Queries;
+using DigitalData.MessagingService.Domain.Entities;
+using DigitalData.MessagingService.Domain.Exceptions;
+using MediatR;
+using Microsoft.Extensions.Logging;
+using System.Text.Json.Serialization;
 
 namespace DigitalData.MessagingService.Application.EmailSending.Commands;
 
@@ -14,7 +17,7 @@ namespace DigitalData.MessagingService.Application.EmailSending.Commands;
 /// </summary>
 public record PublishEmailCommand : IRequest<Guid>
 {
-    public required GetSenderQuery Sender { get; init; }
+    public required GetEmailAccountQuery Sender { get; init; }
 
     /// <summary>
     /// Recipient email addresses
@@ -51,13 +54,17 @@ public record PublishEmailCommand : IRequest<Guid>
 /// Handler for PublishEmailCommand
 /// Resolves the sender account via MediatR, maps to SendingEmailEvent and enqueues to RabbitMQ
 /// </summary>
-public class PublishEmailCommandHandler(ISender Sender, ISendingEmailPublisher Publisher, IMapper Mapper) : IRequestHandler<PublishEmailCommand, Guid>
+public class PublishEmailCommandHandler(IRepository<EmailAccount> Repo, ISendingEmailPublisher Publisher, IMapper Mapper, ILogger<PublishEmailCommandHandler> Logger) : IRequestHandler<PublishEmailCommand, Guid>
 {
     public async Task<Guid> Handle(PublishEmailCommand request, CancellationToken cancellationToken)
     {
-        var senderAccount = await Sender.Send(request.Sender, cancellationToken)
-            ?? throw new NotFoundException(
-                $"No email account found for the given sender criteria (Id: {request.Sender.Id}, Username: {request.Sender.Username}).");
+        var senderAccounts = await Repo.FindAsync(request.Sender.Id is int id ? x => x.Id == id : x => x.Username == request.Sender.Username, cancellationToken: cancellationToken);
+
+        if (senderAccounts.Count() > 1)
+            Logger.LogWarning("Multiple email accounts found for the given criteria ({Criteria}). Returning the first one.", request.Sender.Id is not null ? $"Id: {request.Sender.Id}" : $"Username: {request.Sender.Username}");
+
+        var senderAccount = senderAccounts.FirstOrDefault()
+            ?? throw new NotFoundException($"No email account found for the given sender criteria (Id: {request.Sender.Id}, Username: {request.Sender.Username}).");
 
         var email = Mapper.Map<EmailContext>(request) with { Sender = senderAccount };