Templates more flexible #1327

Is your feature request related to a problem? Please describe.
I want to generate more than just XyzResolver interfaces.
Like XyzResolverImpl and XyzService interfaces.

Describe the solution you'd like

1. A few more variables in the templates.

• The className without the suffix.
• The type of the operation (Mutation, Query, Subscription), so I can generate the @SchemaMapping annotation.

2. A way to generate these into their own files and directories.

Current workarounds

1. I can split the current className by using ?keep_before("Resolver"). That works but bloats the template, since that's done in numerous places.
   But generating the @SchemaMapping is currently impossible I think, as I have no way of knowing the type.

2. Currently I just have them in one file. That's not so bad and is not a priority, but it would be very nice to expand this even further in the future, so that eg. the service interfaces lie in their own package. A generic mechanism would be awesome so you could generate variable amounts of files into variable directories without having them hard coded as model and api.