Since both projects are developed together and by the same team, we also want to have the same code structure and utility methods available in both projects. Therefore, this commit changes many files, but without a functional change.
The RfC Visibility of a consumer is intended to restrict who can access which RfCs. So far, those restrictions were only applied one way, for learners of a restricted consumer to view other (external) RfCs. However, the other way around should also work: If a RfC was created as part of a restricted consumer, no other external user should be able to interfere with this RfC. This commit, therefore, adds this direction as well and covers both directions with tests.
