New Web Service. Choose repo via URL.
Set environment variables:
GOOGLE_CLIENT_ID="______.apps.googleusercontent.com"
GOOGLE_CLIENT_SECRET="______"
GOOGLE_CALLBACK_URL="https://YOUR_RENDER_APP.onrender.com/auth/google/callback"
GOOGLE_CREDENTIALS_FILEPATH="/etc/secrets/google-credentials.json"
SESSION_SECRET="YOUR SECRET HERE"
Set "google-credentials.json" file as a secret. The service will then have access to the file as "/etc/secrets/google-credentials.json".
Under credentials for your web client, configure a redirect url pointing to the render server: "https://YOUR_RENDER_APP.onrender.com/auth/google/callback" and save.
While the web client is in test mode, only tests users can use in production. In the oauth consent screen, add your email address as a "Test User"