Document known issues and workarounds for them
There are some unusual use cases which might not be supported for various reasons. They usually either have a workaround or a user can reset the migrated data for a specified plugin and run migration again.
It might be helpful to document such unusual workflows, in case someone runs in them.
If a user chooses not to migrate all importers or distributors for the initial run, they can't add them to the plan later if there are no changes in pulp 2 (due to optimizations based on time those will be skipped).
Workaround: update resource in pulp 2 or reset the plugin in pulp3.