ra-data-graphql-simple: export internal methods to allow for more customization

[dricholm]

Resolves #9278, same as #9279 but targeting next instead of master

Problem

Without writing a complete build query factory it's not possible to customize ra-data-graphql-simple's default build query. If we only want to modify the response parser for example, we would need to write build GraphQL query and variables logic as well.

Solution

Export buildQueryFactory, buildGqlQuery, buildVariables and getResponseParser from the package to allow for more granular customization.

[slax57]

Thanks!

[Myou5uf]

Hello everyone. You can demonstrate an example of configuration using these features. I don't quite understand how this can be used. Thanks