- Replaced explicit envelope and receiver expression filters with a single `.Where(request)` call.
- Removed redundant checks for null and empty values in handler.
- Updated using statements to include `EnvelopeGenerator.Application.Extensions`.
- Maintains the same functionality while reducing code complexity.
- Introduced `SaveDocStatusAsync` extension method on IMediator to simplify saving document status
- Added `SignDocAsync` extension method as a shortcut for signing document status
- Refactored `SaveDocStatusCommand` usage to support new mediator extension
- Added support for filtering by Envelope.Id or Envelope.Uuid
- Added support for filtering by Receiver.Id, Receiver.EmailAddress, or Receiver.Signature
- Throw BadRequestException when required identifiers are missing
- Updated repository queries to combine envelope and receiver filters
