Allow add-on users to be added to security levels in team managed projects

In team-managed projects security levels or issue restrictions can be enabled; however, this causes add-on users to be unable to see the issues that have restrictions applied.

An example is Automation. When a team-managed issue has restrictions enabled then the Automation user cannot see those issues.

By default, add-on users do not appear in the access configuration page to assign them roles. This causes automation rules to fail without being able to make them work unless the issue restrictions are removed.