Add OAuth2 authentication (#147)

- Added Site settings > Authentication section
- Create/edit/delete your custom oauth2 configurations
- Login or signup with oauth2

docker-compose.yml

@@ -13,6 +13,7 @@ services:
       dockerfile: ./docker/app/Dockerfile
     environment:
       - UPDATE=0
+      - BASE_URL
       - ENVIRONMENT
       - SECRET_KEY_BASE
       - POSTGRES_USER