refactor(graph-gateway): query settings as a request extension

[LNSD]

Use HTTP request extensions to pass request-bound settings, in this case, the auth query settings.

• Decouple QuerySettings from the auth module. Moved to its parent module, client_query.
• Extract the query settings at the parse_auth_token() step.
• Pass the query settings to the handler via request extensions if the auth schema specifies them.
• Check if the subscription exists during subscriptions::parse_auth_token() step. If no subscriptions associated with the bearer token exist, bailout at the require_auth middleware.

[Theodus]

LGTM