docs: add ADR for glob support for role assignments

[BryanttV]

Related issue: #172

Description

This PR adds ADR 0012 - Glob Support For Role Assignments, proposing an extension to the authorization model (Casbin) so that role assignments (g policies) can use glob-like matching in the scope field.

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Check off if complete or not applicable:

• Version bumped
• Changelog record added
• Documentation updated (not only docstrings)
• Fixup commits are squashed away
• Unit tests added/updated
• Manual testing instructions provided
• Noted any: Concerns, dependencies, migration issues, deadlines, tickets

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[bmtcril]

Can you add a little more about the scope boundaries and how they are determined? Also exactly where a suffix can begin? Specifically I'd like to document which of these scopes would be considered valid:

• *
• c*
• course-*
• course-v1*
• course-v1:*
• course-v1:O*
• course-v1:OpenedX+* (already listed, and I assume the only one that would be valid?)

Similarly I'd like to be explicit about whether these comparisons are case-sensitive or not.

[bmtcril]

I assume these would be different per scope type matcher, but would just like to be explicit about the best practices and how we're choosing to reject globs in scopes that don't have custom matchers.

[bmtcril]

Just a couple of comments