[BUG] Container token secret error

[git-hyagi]

Describe the bug
Panic when trying to configure container token:

pulp [ea43c64ce37f4cb1a7fd13a579446490]: django.request:ERROR: Internal Server Error: /token/
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.8/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python3.8/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/django/views/generic/base.py", line 70, in view
    return self.dispatch(request, *args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 509, in dispatch
    response = self.handle_exception(exc)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 469, in handle_exception
    self.raise_uncaught_exception(exc)
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 480, in raise_uncaught_exception
    raise exc
  File "/usr/local/lib/python3.8/site-packages/rest_framework/views.py", line 506, in dispatch
    response = handler(request, *args, **kwargs)
  File "/usr/local/lib/python3.8/site-packages/pulp_container/app/registry_api.py", line 372, in get
    data = authorization_service.generate_token()
  File "/usr/local/lib/python3.8/site-packages/pulp_container/app/authorization.py", line 69, in generate_token
    with open(settings.PUBLIC_KEY_PATH, "rb") as public_key:
IsADirectoryError: [Errno 21] Is a directory: '/etc/pulp/keys/container_auth_public_key.pem'

To Reproduce
Steps to reproduce the behavior:
Configure Pulp CR with container token auth:

...
spec:
  container_auth_private_key_name: container_auth_private_key.pem
  container_auth_public_key_name: container_auth_public_key.pem
  container_token_secret: pulp-container-auth
...

make a request to token service:

$ PULP_PWD=$(oc extract secret/pulp-admin-password --to=-)
$ oc exec deployment/pulp-api -- curl -i -su admin:${PULP_PWD}  'http://localhost:24817/token/?service=api'
HTTP/1.1 500 Internal Server Error
Server: gunicorn
Date: Mon, 19 Dec 2022 17:50:03 GMT
Connection: close
Content-Type: text/html
X-Frame-Options: DENY
Content-Length: 145
X-Content-Type-Options: nosniff
Referrer-Policy: same-origin
Correlation-ID: d324945d0260416abdd299144fb93841
Access-Control-Expose-Headers: Correlation-ID

the panic from the issue description will appear in pulp-api pod logs.