🔧(backend) configure Authorization Code authentication

Integrate 'mozilla-django-oidc' dependency, to support
Authorization Code flow, which is required by Agent Connect.

Thus, we provide a secure back channel OIDC flow, and return
to the client only a session cookie.

Done:
- Replace JWT authentication by Session based authentication in DRF
- Update Django settings to make OIDC configurations easily editable
- Add 'mozilla-django-oidc' routes to our router
- Implement a custom Django Authentication class to adapt
'mozilla-django-oidc' to our needs

'mozilla-django-oidc' routes added are:
- /authenticate
- /callback (the redirect_uri called back by the Idp)
- /logout

.github/workflows/publish.yml

@@ -130,7 +130,7 @@ jobs:
       DJANGO_CONFIGURATION: Test
       DJANGO_SETTINGS_MODULE: publish.settings
       DJANGO_SECRET_KEY: ThisIsAnExampleKeyForTestPurposeOnly
-      DJANGO_JWT_PRIVATE_SIGNING_KEY: ThisIsAnExampleKeyForDevPurposeOnly
+      OIDC_OP_JWKS_ENDPOINT: /endpoint-for-test-purpose-only
       DB_HOST: localhost
       DB_NAME: publish
       DB_USER: dinum