Add support for fetching document metadata separately

Introduced a new `ReadDocumentDetailsQuery` to fetch document
metadata (`DocumentDetailsDto`) without the binary payload.
Updated `MappingProfile` to map `Document` to `DocumentDetailsDto`.

Refactored `DocumentService` to handle separate fetching of
metadata and binary data, combining them into `DocumentDto`.
Changed the metadata endpoint to `/api/Document/details`.

Added a new `GetDocumentDetails` endpoint in `DocumentController`
to return metadata without binary data. Updated
`EnvelopeReceiverPageDataService` with a new method
`GetDocumentMetadataOfSenderAsync` for fetching metadata.

These changes improve efficiency by allowing clients to load
metadata without transferring large binary data when unnecessary.

EnvelopeGenerator.Server/EnvelopeGenerator.Server/Controllers/DocumentController.cs

@@ -31,17 +31,30 @@ public class DocumentController(IMediator mediator, IAuthorizationService authSe
     /// <param name="cancel">Cancellation token.</param>
     [HttpGet]
     [Authorize(AuthenticationSchemes = AuthScheme.Sender)]
-    public async Task<IActionResult> GetDocument(CancellationToken cancel, [FromQuery] ReadDocumentQuery? query = null)
+    public async Task<IActionResult> GetDocument(CancellationToken cancel, [FromQuery] ReadDocumentQuery query)
     {
-        if (query is null)
-            return BadRequest("Missing document query.");
-
         var senderDoc = await mediator.Send(query, cancel);
         return senderDoc?.ByteData is byte[] senderDocByte
             ? File(senderDocByte, "application/octet-stream")
             : NotFound("Document is empty.");
     }
 
+    /// <summary>
+    /// Returns sender document metadata and element details (without binary payload) for editor loading.
+    /// </summary>
+    /// <param name="query">Document query with EnvelopeId.</param>
+    /// <param name="cancel">Cancellation token.</param>
+    [HttpGet("details")]
+    [Authorize(AuthenticationSchemes = AuthScheme.Sender)]
+    public async Task<IActionResult> GetDocumentDetails(CancellationToken cancel, [FromQuery] ReadDocumentDetailsQuery query)
+    {
+        var senderDoc = await mediator.Send(query with { UserId = User.GetId() }, cancel);
+        if (senderDoc is null)
+            return NotFound("Document is empty.");
+
+        return Ok(senderDoc);
+    }
+
     /// <summary>
     /// Gets the document for the specified envelope key.
     /// </summary>

EnvelopeGenerator.Server/EnvelopeGenerator.Server/Services/EnvelopeReceiverPageDataService.cs

@@ -57,6 +57,14 @@ public class EnvelopeReceiverPageDataService(
         return await mediator.Send(new ReadDocumentQuery(EnvelopeId: envelopeId, UserId: user.SenderId()), cancellationToken);
     }
 
+    /// <summary>
+    /// Loads document metadata/elements for the authenticated sender without binary payload.
+    /// </summary>
+    public async Task<DocumentDetailsDto?> GetDocumentMetadataOfSenderAsync(ClaimsPrincipal user, int envelopeId, CancellationToken cancellationToken = default)
+    {
+        return await mediator.Send(new ReadDocumentDetailsQuery(EnvelopeId: envelopeId, UserId: user.SenderId()), cancellationToken);
+    }
+
     /// <summary>
     /// Loads the current receiver's signature placeholders.
     /// </summary>