Validate the external authorization is only called once per request

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We should avoid multiple calls to the external authorization service within a single request.

Since the call could be triggered by a simple can?(current_user, :read_project, project) it's easy to miss a new call.

We could use the RequestStore in development & test to track the number of calls and raise an exception if it occurs more than once.

Edited by 🤖 GitLab Bot 🤖