Make authority a unique index on modUserGroupRole

[opengeek]

What does it do?

Adds a unique index to the modUserGroupRole.authority field.

Why is it needed?

modUserGroupRole records are linked to ACLs via the authority value, so those MUST be unique or referential integrity is lost.

How to test

Run the transport build, execute the setup, and verify that after adding a modUserGroupRole record with a non-unique authority value, the upgrade stops with a failure describing what you need to do in order to resolve the situation before re-running the setup. After removing the non-unique record, verify that setup then runs successfully and a unique index is added to the authority column.

Related issue(s)/PR(s)

This is related to and should be adopted along with #16568 — see discussion on that PR.