compose_client version negotiation

[s4ke]

We need a way to do version negotiation between a) the server and the client and b) the dumped files and the client. Otherwise, the client and the server need to be updated in lockstep which is not the nicest of experiences.

[s4ke]

In the meantime we switch behaviour to "EXCLUDE" instead of "RAISE" for undefined to not cause issues starting from 2.1.0