registry: Namespace support for orgs

[kpcyrd]

There's currently no way for a github org to publish in their namespace, because the sn0int registry authenticates the github username through oauth (which can't be done for orgs, even if the user owns that org).

A github org should be able to use their namespace as well, the challenges are:

• it's not obvious how to check if the user belongs to the org
• even if the user belongs to the org, the org may not want to grant publish permissions to every user.

One possible solution (if no better solution can be found) would be a repository that's fetched from 'https://github.com/ORG_NAME/sn0int-auth` that lists the github users that are allowed to publish in ORG_NAME.

This repo could also contain encrypted auth keys that don't belong to a specific user so it's possible to publish modules with github actions.

As mentioned in sysdogs/sn0int-modules#2