Limit Tag Creation To Staff

Both of these dropdowns should have a “Staff” option:

As discussed here:

Thank you!

cc @neil

「いいね!」 8

Sounds good to me @neil, whenever you want to get to it.

「いいね!」 3

Should we include staff and admin groups in trust levels?

「いいね!」 2

Probably staff vs not-staff is fine for now, we can make it more granular later if people ask for that.

「いいね!」 5

I added a new enum type TrustLevelAndStaffSetting.

https://github.com/discourse/discourse/pull/6023

「いいね!」 7