Deprecate methods and streamline controller code

Added [Obsolete("Use MediatR")] attribute to several methods
across `DocumentController`, `HomeController`,
`TestConfigController`, `TestDocumentReceiverElementController`,
and `TestEnvelopeController` to indicate they should no longer
be used.

Refactored constructors in `TestConfigController` and
`TestEnvelopeController` to remove unnecessary empty blocks.

Improved formatting and structure of the `GetAll` method in
`TestEnvelopeController` for better clarity while maintaining
functionality.

Updated `Program.cs` to suppress warnings about obsolete
types/members during service registrations, indicating a
transition to newer implementations.

EnvelopeGenerator.Web/Controllers/DocumentController.cs

@@ -26,6 +26,7 @@ public class DocumentController : BaseController
         _envDocService = envDocService;
     }
 
+    [Obsolete("Use MediatR")]
     [NonAction]
     public async Task<IActionResult> Get([FromRoute] string envelopeKey, [FromQuery] int index)
     {
@@ -53,6 +54,7 @@ public class DocumentController : BaseController
 
     [Authorize(Roles = ReceiverRole.FullyAuth)]
     [HttpPost("{envelopeKey}")]
+    [Obsolete("Use MediatR")]
     public async Task<IActionResult> Open(string envelopeKey)
     {
         try