Feat: Implement Google OAuth using django-allauth for user social authentication

[pankaj-basnet]

PR Description: This PR implements social authentication using the OAuth 2.0 framework via django-allauth, specifically configuring the Google provider.

Proposed Changes

• Authentication Flow: Implements the OAuth 2.0 Authorization Code flow for secure user sign-in and account linking.

Related Issue(s)

• supports OIDC Authentication: Add OIDC Integration #1797

Actions Performed:

• Verified successful redirect to Google Account Selector.
• Confirmed automatic user creation/login upon successful OAuth callback.
• Validated that the setup_google_oauth command correctly populates the allauth's socialaccount_socialapp table.

[pankaj-basnet]

also made demo sample django+react project to show google oauth authentication. https://github.com/pankaj-basnet/Google-oauth-authentication---Django-and-React

[rolandgeider]

there's some tests failing:

[1](https://github.com/wger-project/wger/actions/runs/24082190974/job/70245437796?pr=2271#step:8:10742)
  File "/home/runner/work/wger/wger/.venv/lib/python3.11/site-packages/allauth/socialaccount/adapter.py", line 212, in get_provider
    app = self.get_app(request, provider=provider, client_id=client_id)
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/work/wger/wger/.venv/lib/python3.11/site-packages/allauth/socialaccount/adapter.py", line 302, in get_app
    raise SocialApp.DoesNotExist()
allauth.socialaccount.models.SocialApp.DoesNotExist

do we need to register them somehow first?

edit: nevermind, just saw in your other repo that we need to run manage.py setup_google_auth. Can you explain a bit how to get the YOUR_CLIENT_ID and YOUR_CLIENT_SECRET

[rolandgeider]

something else, we should hide this behind a config option, so that this is not shown e.g. in local deployments where it's not used