Provide warning about group import in progress
With ~"Importer:GitLab Migration" growing in terms of what entities are imported it obviously takes more & more time between the event of group creation and actual import being completed.
For project imports we completely lock ability to do any actions, which might not be a good idea for groups - since import might take hours for big groups.
My suggestion is to introduce warning banner, that group you're currently looking at is currently being imported and link to group import status page (which will be implemented in #285577 (closed))
@hdelalic as always, I'm open for better wording suggestion.
frontend here is pretty trivial, but I will need @gitlab-org/manage/import/backend hand to understand where & how to get this data - if it is just a field for group, or (as I believe) it will require a bit more complex logic, since we might be viewing at subgroup of group being imported