Returns authentication credentials sent by the user with the particular message.
Reference to MCMessageCredentials associated with the message.
Call this method to get authentication credentials sent with the message. The returned value corresponds to credentials which were passed to OnValidateCredentials. Use this method from message handling code.
If invalid message reference is passed (eg. the message has been already processed), null/nil/nothing is returned.
Note: the method doesn't create a new object but returns a reference to existing object. You should not alter or deallocate the returned object and its fields.