Revert "Simplify discussion/tag permission logic"
Revert "Simplify discussion/tag permission logic"

This reverts commit 01e776e2bec2a0d9b112ca7979a1945ec553a346.

Turns out that there was a good reason for the original logic... the case of per-tag moderators.

flarum/tags,flarum/tags,flarum/tags