API: a scope with access to /uploads

[RogerBW]

@david

@RogerBW are you willing/able to make a PR here? If so, please do go ahead, and then post the link in this topic.

Done. It will need testing and such but here at least is a baseline.

https://github.com/discourse/discourse/pull/14941

I used a separate scope, for the reasons described - I can certainly see that I might want to allow posts but not uploads.