Refactor claim handling and simplify controllers

Refactored multiple controllers (`AnnotationController`,
`DocumentController`, `ReadOnlyController`, and
`SignatureController`) to use updated claim extension methods
(`ReceiverSignature`, `EnvelopeUuid`, etc.), replacing older,
verbose methods for improved readability and consistency.

Removed the `EnvelopeClaimTypes` class and replaced claim type
constants with `EnvelopeClaimNames`. Simplified claim retrieval
logic in `ReceiverClaimExtensions` by consolidating methods and
removing redundant or unused functionality.

Eliminated the `SignInEnvelopeAsync` method, indicating a shift
away from manual claim management. Performed general cleanup,
including removing obsolete code and improving exception
messages for better debugging context.

EnvelopeGenerator.API/Controllers/ReadOnlyController.cs

@@ -41,14 +41,14 @@ public class ReadOnlyController : ControllerBase
     [Obsolete("Use MediatR")]
     public async Task<IActionResult> CreateAsync([FromBody] EnvelopeReceiverReadOnlyCreateDto createDto)
     {
-        var authReceiverMail = User.GetReceiverMailOfReceiver();
+        var authReceiverMail = User.ReceiverMail();
         if (authReceiverMail is null)
         {
             _logger.LogError("EmailAddress claim is not found in envelope-receiver-read-only creation process. Create DTO is:\n {dto}", JsonConvert.SerializeObject(createDto));
             return Unauthorized();
         }
 
-        var envelopeId = User.GetEnvelopeIdOfReceiver();
+        var envelopeId = User.EnvelopeId();
 
         createDto.AddedWho = authReceiverMail;
         createDto.EnvelopeId = envelopeId;