backend/app/auth/oauth.py

from authlib.integrations.starlette_client import OAuth
from starlette.config import Config
from app.core.config import settings

config = Config(environ={
    "GOOGLE_CLIENT_ID": settings.GOOGLE_CLIENT_ID,
    "GOOGLE_CLIENT_SECRET": settings.GOOGLE_CLIENT_SECRET
})

oauth = OAuth(config)
oauth.register(
    name='google',
    server_metadata_url='https://accounts.google.com/.well-known/openid-configuration',
    client_kwargs={
        'scope': 'openid email profile'
    }
)