- Added `HasFilter` property to check if any filter parameters are provided.
- Implemented `ThrowIfHasNoFilter()` method to enforce at least one filter parameter.
- Improves robustness and validation of RemoveSignatureNotification.
Added optional parameters `EnvelopeId` and `ReceiverId` to RemoveSignatureNotification
to provide additional context when removing receiver signatures.
Added a new nullable ReceiverSignature property to the RemoveSignatureNotification record
to support handling receiver-specific signature removal events.