Refactor email account handling for dynamic resolution

Reintroduced `EmailAccountDto` with conditional compilation to support both .NET and non-.NET environments. Updated `IEmailService` to accept `EmailAccountDto` as the sender, replacing reliance on pre-configured SMTP credentials.

Added `GetSenderQuery` and its handler to dynamically resolve email accounts based on `Id` or `Username`. Introduced `GetSenderQueryValidator` for validation, ensuring proper usage of the query.

Modified `SendEmailCommand` to include sender resolution via MediatR. Updated `OutgoingEmailEvent` to include sender information and adjusted `OutgoingEmailConsumer` and `LimilabsEmailService` to use the dynamically resolved sender.

Updated `EmailMappingProfile` to ignore the `Sender` property during mapping. Replaced `Name` with `Id` in `appsettings.Secrets.json` for email accounts. Removed the old `EmailAccountDto` folder and performed general cleanup and restructuring.

src/core/DigitalData.MessagingService.Application/Common/Dtos/EmailAccountDto.cs

@@ -1,27 +0,0 @@
-namespace DigitalData.MessagingService.Application.Common.Dtos;
-
-/// <summary>
-/// DTO for a single email account configuration.
-/// </summary>
-public class EmailAccountDto
-{
-    /// <summary>
-    /// Logical name to identify this account (e.g. "default", "support").
-    /// </summary>
-    public int Id { get; init; }
-
-    public required string Username { get; init; }
-
-    public required string Password { get; init; }
-
-    public bool PasswordEncrypted { get; init; } = false;
-
-    public required string SmtpServer { get; init; }
-
-    public int SmtpPort { get; init; }
-
-    public bool SmtpUseSsl { get; init; }
-
-    public bool UseOAuth2 { get; init; }
-}
-

src/core/DigitalData.MessagingService.Application/Common/Interfaces/IEmailService.cs

@@ -1,3 +1,5 @@
+using DigitalData.MessagingService.Application.Common.Dtos;
+
 namespace DigitalData.MessagingService.Application.Common.Interfaces;
 
 /// <summary>
@@ -12,5 +14,5 @@ public interface IEmailService
     /// Sends an email using the configured SMTP account.
     /// SMTP credentials are configured in appsettings.json (EmailAccount section).
     /// </summary>
-    Task SendEmailAsync(string to, string subject, string body, bool isHtml = true, CancellationToken cancellationToken = default);
+    Task SendEmailAsync(EmailAccountDto from, string to, string subject, string body, bool isHtml = true, CancellationToken cancellationToken = default);
 }

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

@@ -12,8 +12,10 @@ public class EmailMappingProfile : Profile
     public EmailMappingProfile()
     {
         // SendEmailCommand -> OutgoingEmailEvent
+        // Sender is resolved via MediatR in the handler and set separately after mapping.
         CreateMap<SendEmailCommand, OutgoingEmailEvent>()
             .ForMember(dest => dest.Id, opt => opt.MapFrom(_ => Guid.NewGuid()))
-            .ForMember(dest => dest.QueuedAt, opt => opt.MapFrom(_ => DateTime.Now));
+            .ForMember(dest => dest.QueuedAt, opt => opt.MapFrom(_ => DateTime.Now))
+            .ForMember(dest => dest.Sender, opt => opt.Ignore());
     }
 }