Associate tokens with a namespace instead of a user

[bdeitte]

Right now, tokens are associated with users, and if the person is no longer a member of the namespace, the token stops functioning. It would be better for automated workflows to allow for tokens that are associated just with a namespace.

This request is similar but different from #957 which is concerned with the scope.

[bdeitte]

I chatted with someone here about this, and I can understand you don't want to do it for security reasons- personally, I think you could do this if the namespace tokens are available to all admins so they can be revoked if needed. Let me know if you would be interested on this and I may poke around for it to see if something could work.