Don't create namespaces that don’t exist when importing project using GitHub import Rake task
Problem to solve
Recently we have changed the behaviour of the GitHub importer to not create any missing intermediate namespaces (groups) if they do not exist. Therefore, the user needs to provide an existing namespace which can be their own user namespace or an existing group that they have permission to import a project into.
These changes affected only importing via UI and API. Now we want to change the behaviour of GitHub import Rake task as well.
Proposed solution
The user needs to provide an existing namespace which can be their own user namespace or an existing group that they have permission to import a project into. If the condition don't match, we should return an error to the user before creating or importing anything.
In other words, if user wants to import to a group and has no group on GitLab they can import into, they should first create a group.
Documentation
Following user documentation should be updated with the changes implemented in this issue: