init SendMailHandler to read tempalte and replace placeholders

EnvelopeGenerator.Application/Documents/Queries/ReadDocumentQuery.cs

@@ -22,7 +22,7 @@ public record ReadDocumentQuery(int? Id = null, int? EnvelopeId = null) : IReque
 public class ReadDocumentQueryHandler : IRequestHandler<ReadDocumentQuery, EnvelopeDocumentDto?>
 {
     /// <summary>
-    /// Repository for accessing <see cref="EnvelopeDocument"/> entities.
+    /// TempRepo for accessing <see cref="EnvelopeDocument"/> entities.
     /// </summary>
     private readonly IRepository<EnvelopeDocument> _repo;