/s

Simplify IMAP email fetching API and refactor logic

Removed `markAsSeen` parameter from `FetchEmailsAsync` and
`FetchEmailByUidAsync` methods in `IImapEmailService` to
simplify the API. Updated `MailSearchFilter` to make `MaxCount`
nullable for greater flexibility.

Removed `markAsSeen` from `FetchEmailByUidQuery` and
`FetchEmailsQuery` records and their handlers. Deleted
`FetchEmailByUidQueryValidator` as it is no longer needed.

Refactored `LimilabsImapEmailService`:
- Introduced `FetchEmailUidsAsync` to centralize UID fetching logic.
- Simplified `FetchEmailByUidAsync` using a new helper method.
- Consolidated connection, authentication, and folder selection
  into reusable private methods.
- Removed redundant code for search criteria and flag fetching.

Removed `IsSeen` from `ReceivedEmailContext` and improved
overall code readability and maintainability by reducing
duplication and centralizing logic.

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

@@ -13,7 +13,6 @@ public interface IImapEmailService
     /// </summary>
     /// <param name="account">Account whose IMAP settings will be used.</param>
     /// <param name="filter">Filter to apply when fetching emails.</param>
-    /// <param name="markAsSeen">
     /// When <see langword="true"/> (default), fetched messages are marked as <c>\Seen</c> on the server.
     /// Set to <see langword="false"/> for a non-destructive read (uses <c>BODY.PEEK</c> internally).
     /// </param>
@@ -21,7 +20,6 @@ public interface IImapEmailService
     Task<IEnumerable<ReceivedEmailContext>> FetchEmailsAsync(
         EmailAccountDto account,
         MailSearchFilter filter,
-        bool markAsSeen = true,
         CancellationToken cancellationToken = default);
 
     /// <summary>
@@ -35,7 +33,6 @@ public interface IImapEmailService
     /// <summary>
     /// Fetches a single email by its UID.
     /// </summary>
-    /// <param name="markAsSeen">
     /// When <see langword="true"/> (default), the message is marked as <c>\Seen</c> on the server.
     /// Set to <see langword="false"/> for a non-destructive read.
     /// </param>
@@ -44,7 +41,6 @@ public interface IImapEmailService
         long uid,
         string folder = "INBOX",
         bool withAttachments = false,
-        bool markAsSeen = true,
         CancellationToken cancellationToken = default);
 
     /// <summary>

src/core/DigitalData.MessagingService.Application/Common/Models/MailSearch/MailSearchFilter.cs

@@ -29,7 +29,7 @@ public record MailSearchFilter
     /// Maximum number of messages to retrieve. <c>0</c> means unlimited.
     /// Applied after sorting; defaults to <c>50</c>.
     /// </summary>
-    public int MaxCount { get; init; } = 50;
+    public int? MaxCount { get; init; } = null;
 
     /// <summary>
     /// Controls the order of the returned messages. Defaults to <see cref="MailSortOrder.NewestFirst"/>.

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

@@ -36,11 +36,6 @@ public record FetchEmailByUidQuery : IRequest<ReceivedEmailContext?>
     /// When <see langword="true"/>, attachment data is included in the result.
     /// </summary>
     public bool WithAttachments { get; init; } = false;
-    /// <summary>
-    /// When <see langword="true"/> (default), the message is marked as <c>\Seen</c> on the server.
-    /// Set to <see langword="false"/> for a non-destructive peek.
-    /// </summary>
-    public bool MarkAsSeen { get; init; } = true;
 }
 
 public class FetchEmailByUidQueryHandler(
@@ -62,7 +57,6 @@ public class FetchEmailByUidQueryHandler(
             (long)request.Uid!,
             request.Folder,
             request.WithAttachments,
-            request.MarkAsSeen,
             cancellationToken);
     }
 }

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

@@ -21,12 +21,6 @@ public record FetchEmailsQuery : IRequest<IEnumerable<ReceivedEmailContext>>
     /// Mail query used to filter and limit the emails retrieved.
     /// </summary>
     public MailSearchFilter Mail { get; init; } = new();
-
-    /// <summary>
-    /// When <see langword="true"/> (default), fetched messages are marked as <c>\Seen</c> on the server.
-    /// Set to <see langword="false"/> for a non-destructive peek.
-    /// </summary>
-    public bool MarkAsSeen { get; init; } = true;
 }
 
 public class FetchEmailsQueryHandler(
@@ -46,7 +40,6 @@ public class FetchEmailsQueryHandler(
         return await ImapService.FetchEmailsAsync(
             account,
             request.Mail,
-            request.MarkAsSeen,
             cancellationToken);
     }
 }

src/core/DigitalData.MessagingService.Application/EmailReceiving/Validators/FetchEmailByUidQueryValidator.cs

@@ -1,27 +0,0 @@
-using DigitalData.MessagingService.Application.EmailReceiving.Queries;
-using FluentValidation;
-
-namespace DigitalData.MessagingService.Application.EmailReceiving.Validators;
-
-/// <summary>
-/// Validates a <see cref="FetchEmailByUidQuery"/> before it is handled by <see cref="FetchEmailByUidQueryHandler"/>.
-/// </summary>
-public class FetchEmailByUidQueryValidator : AbstractValidator<FetchEmailByUidQuery>
-{
-    public FetchEmailByUidQueryValidator()
-    {
-        RuleFor(x => x.Account)
-            .NotNull()
-            .WithMessage("Account query must not be null.");
-
-        RuleFor(x => x.Uid)
-            .NotNull()
-            .WithMessage("UID must be provided. Use WithUid() to set the UID before dispatching the query.")
-            .GreaterThan(0)
-            .WithMessage("UID must be greater than 0.");
-
-        RuleFor(x => x.Folder)
-            .NotEmpty()
-            .WithMessage("Folder must not be empty.");
-    }
-}