Remove generic id from Message

[bitzl]

The Message interface has a generic type for an identifier attribute. Due to complex nested generics and different possible implementations, this generic type is mostly ommitted. At the same time, the interface's T getId() is never used outside of unit tests.

Applications build upon the framework are strongly encouraged to implement their own message classes and would not rely on the id property. There are applications that won't use the id property at all.

Suggested solution
Is it possible to remove the ID getId() property and the generic type parameter from the Message interface?

Now:

public interface Message<ID> {

  Envelope getEnvelope();

  ID getId();
}

New:

public interface Message {

  Envelope getEnvelope();

}

[bitzl]

Resolved by #165