This should probably be an upgrade task. It is possible that some users will have specific OSUser solutions in place and will not want the upgrade task to run. We should identify a way for users to avoid running this upgrade task if it is unwanted, or not use an upgrade task but simply provide a porting utility.

Users who do not want to migrate immediately will be introduced to a migrating plan, to help them port their OSUser dependent code to Atlassian User.