🔧(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

Dockerfile

@@ -55,7 +55,7 @@ COPY ./src/backend /app/
 WORKDIR /app
 
 # collectstatic
-RUN DJANGO_CONFIGURATION=Build DJANGO_JWT_PRIVATE_SIGNING_KEY=Dummy \
+RUN DJANGO_CONFIGURATION=Build \
     python manage.py collectstatic --noinput
 
 # Replace duplicated file by a symlink to decrease the overall size of the