This commit introduces the `[Obsolete("Use MediatR")]` attribute to various service fields and methods across multiple controllers and extension classes, signaling a transition to MediatR for handling requests and commands.
Key changes include:
- Marking `IEnvelopeService`, `IEnvelopeReceiverService`, and `IEnvelopeTypeService` as obsolete in their respective controllers.
- Updating `AddEnvelopeGeneratorInfrastructureServices` to utilize `IRepository`.
- Refactoring `AddCommandManagerRunner` and `CreateHost` methods to indicate obsolescence.
- Replacing `DigitalData.Core.DTO` with `DigitalData.Core.Abstraction.Application.DTO` in using directives.
These changes modernize the codebase and improve command and query handling while cleaning up service dependencies.