Make sure the permission calculator works for non-current-user accounts

Currently, the current user context is being used. This does not work because we return the result of the current user even if asking for the group permissions of another user.

In order to fix this, we will:

1. Still use the user cache context internally in the variation cache call but use the account switcher to temporarily set it to the right account.
2. Make sure no internal cache contexts bubble up by simply not adding them to the calculated permissions (this was a mistake/bug)