Add to the executor's context

[molexx]

Now we have schema merging we can add non-JPA functionality to our projects. Sometimes that functionality needs some things in the context - set in the executor and available from DataFetchingEnvironment. But graphql-jpa-query defines the Executor which runs all calls and I don't see how to modify that context without breaking it.

In my particular case I need the HttpServletRequest used to make the query call. Maybe other use cases might want to add their own things in there?

[igdianov]

@molexx I think I can expose ExecutionContext via Builder Factory, so you could inject your own stuff in it easily as well as access HttpServletRequest. The reason it is closed is that I had to make a hack in earlier graphql-java library version to inject variables value for resolving bindings in reverse query fields. I think in graphql-java:11 I can now resolve variables without that hack and expose ExecutionContext customization for schema extensions.

Stay tuned for PR.