Messages - Clarification needed on "never reassigned" for user_id

[Michael Jones]

Never reassigned in what context? Just for that authorization endpoint? For all users across all authorization endpoints for all time?

The spec doesn't say, and it needs to.

[Nat Sakimura]

Fix #328 Clarify the uniquness/never-reassignedness of user_id.

→ 059c2e2f9eff