Run a migration job after changing the storage backend

[git-hyagi]

Describe the bug
Modifying the storage backend in settings.py without running a migration will break the downloads:

[2024-03-26 21:00:54 +0000] [30] [ERROR] Error handling request
Traceback (most recent call last):
File "/usr/local/lib64/python3.9/site-packages/aiohttp/web_protocol.py", line 452, in _handle_request
resp = await request_handler(request)
File "/usr/local/lib64/python3.9/site-packages/aiohttp/web_app.py", line 543, in _handle
resp = await handler(request)
...
File "/usr/local/lib/python3.9/site-packages/django/core/files/storage/base.py", line 121, in path
raise NotImplementedError("This backend doesn't support absolute paths.")
NotImplementedError: This backend doesn't support absolute paths.

To Reproduce
Steps to reproduce the behavior:

• install Pulp with a Storage Class or PVC
• update the CR to use object storage

Expected behavior
The operator should run/create a migration job if the storage backend has been modified.

[git-hyagi]

note: as of now, the artifacts from the old storage will not be copied/migrated to the new storage backend: pulp/pulpcore#3358