Is it possible to make ApolloSubscriptionProtocolHandler more pluggable

[verunder]

This is clearly enhancement/extension request.

Here is the situation description:
Basically, we use different server instead of spring-boot library. Vert.X to be specific.
While ApolloSubscriptionProtocolHandler class is awesome and has all the functionality that I need, it is based off different classes that I have the handle to with Vert.X. (Vert.x web-socket does not implement javax.websocket.Session).

I was wondering if you are open to the possibility of refactoring the ApolloSubscriptionProtocolHandler into something that is more pluggable and does not depend on the javax.websocket.Session(at minimum)? I can help, if necessary.

Sorry if I stepped over the line with this request. :)

[oliemansm]

Definitely open to that. Not sure when I'll be able to work on that, so contributions are welcome too!

[oliemansm]

This will be released in 9.0.0, see #217.