fix(didcomm): handle keylist-update-response from mediator
The SDK sent MediationKeysUpdateList to the mediator but did not process the response, so per-recipient failures reported by the mediator went unnoticed. Register a handler for the keylist-update-response protocol message. Each entry in body.updated is inspected; results other than success or no_change are logged as warnings with the recipient DID and action. Confirmed against the Identus mediator (MediatorCoordinationExecuter.scala) which returns this response with tuples of (recipient_did, action, result). Closes #391 Signed-off-by: Seydi Charyyev <[email protected]>