Naming convention on client side

### Is your proposal related to a problem?

Activating naming convention on server side introduce breaking for lib's tied to default conventions. Like https://github.com/hasura/ra-data-hasura

### Describe the solution you'd like

Allow client to choose naming convention on request by providing additional header like `X-Naming-Convention: `

No file, test, or entry point is named. Start by tracing request handling and existing naming-convention configuration, then define how the proposed X-Naming-Convention header is validated and applied; done means clients can select a convention per request without breaking existing defaults.

Written by the indexing model from the issue text.