Refactor EnvelopeStatus usage and streamline code

- Added `EnvelopeGenerator.Domain.Constants` in multiple files, replacing `Domain.Constants.EnvelopeStatus` with `EnvelopeStatus` for improved readability.
- Modified `CreateEnvelopeCommandHandler.cs` to directly use `request.UserId`, eliminating unnecessary local variable assignment.
- Identified potential duplication in query logic within `ReceiverAlreadySignedQuery.cs`.
- Updated `IEnvelopeService`, `EnvelopeReceiverService`, and `EnvelopeService` to ensure consistent usage of the simplified `EnvelopeStatus`.
- Overall, these changes enhance code maintainability and clarity.

EnvelopeGenerator.Application/Envelopes/Queries/ReadEnvelopeQuery.cs

@@ -1,5 +1,6 @@
 using MediatR;
 using EnvelopeGenerator.Application.Model;
+using EnvelopeGenerator.Domain.Constants;
 
 namespace EnvelopeGenerator.Application.Envelopes.Queries;
 
@@ -48,20 +49,20 @@ public record EnvelopeStatusQuery
     /// <summary>
     /// Der minimale Statuswert, der berücksichtigt werden.
     /// </summary>
-    public Domain.Constants.EnvelopeStatus? Min { get; init; }
+    public EnvelopeStatus? Min { get; init; }
 
     /// <summary>
     /// Der maximale Statuswert, der berücksichtigt werden.
     /// </summary>
-    public Domain.Constants.EnvelopeStatus? Max { get; init; }
+    public EnvelopeStatus? Max { get; init; }
 
     /// <summary>
     /// Eine Liste von Statuswerten, die einbezogen werden.
     /// </summary>
-    public Domain.Constants.EnvelopeStatus[]? Include { get; init; }
+    public EnvelopeStatus[]? Include { get; init; }
 
     /// <summary>
     /// Eine Liste von Statuswerten, die ignoriert werden werden.
     /// </summary>
-    public Domain.Constants.EnvelopeStatus[]? Ignore { get; init; }
+    public EnvelopeStatus[]? Ignore { get; init; }
 }