/users package

IsCanonicalTaken reports whether the given name's canonical form is already registered. Pass the raw name; canonicalization is applied internally. The first return is the original (non-canonical) name that owns the canonical key, for UX in collision messages.

When a bypass write (RegisterUserIgnoreCanonical or the bypass path through ProposeRegisterUser/ProposeUpdateName) overwrites a prior canonical entry, this returns the most-recently-written original.