Django command to migrate worker versions towards generic one

Refs https://redmine.teklia.com/issues/3678

We'll create a new interactive django command to help instance administrators to migrate worker and their versions (for a given repository).

Steps:

1. find generic worker:
   • from CLI input
   • find an existing worker in that repo with name generic
   • ask user for UUID
2. iterate over workers & their versions, excluding the generic worker
   1. find matching model by name
   2. find last model version available
   3. create a worker run for that model version + generic worker
   4. update all ML results to use that worker run + generic worker version

CLI input parameters:

• repo_url, required
• --generic-worker-id, optional worker that is the target belonging to that repo