Update GITHUB.md to reflect Docker setup

docs/GITHUB.md

@@ -1,26 +1,40 @@
 ### GitHub authentication
 
-- [Register a new OAuth application](https://github.com/settings/applications/new)
-    - "Homepage URL" should be the URL you access the frontend on (e.g. `http://localhost:8080`)
-    - "Authorization callback URL" should be the same as the homepage URL, but with `/login` appended
+1. [Register a new OAuth application](https://github.com/settings/applications/new).
 
-- Edit `.env.local`:
-    - Set `GITHUB_CLIENT_ID` to the application client ID
-    - Set `GITHUB_CLIENT_SECRET` to the application client secret (do **not** share this)
+   - Set **Homepage URL** to `http://localhost`.
+   - Set **Authorization callback URL** to `http://localhost/login`.
+   - If you have modified the nginx config, or are running the site on a different host or port, use that URL instead and append `/login` for the callback.
 
-- Restart the server
+2. Edit `backend/docker.dev.env`:
+
+   - Set `GITHUB_CLIENT_ID` to the OAuth application client ID.
+   - Set `GITHUB_CLIENT_SECRET` to the OAuth application client secret. Do not share this value.
+
+3. Edit `.env`:
+
+   - Set `GITHUB_CLIENT_ID` to the OAuth application client ID. The frontend uses this to show the GitHub login button.
+   - You do not need to set `GITHUB_CLIENT_SECRET` here.
+
+4. Restart the frontend and backend services so both environment files are reloaded.
 
 ### Making a user an admin
 
-After signing in with GitHub, you can make yourself an admin with the following:
+After signing in with GitHub, you can make your user an admin from the backend container:
 
+```sh
+docker compose exec backend uv run python manage.py shell
 ```
-$ uv run python3 manage.py shell
->>> from django.contrib.auth.models import User
->>> user = User.objects.get(username="your_username")
->>> user.is_staff = True
->>> user.is_superuser = True
->>> user.save()
+
+Then run:
+
+```py
+from django.contrib.auth.models import User
+
+user = User.objects.get(username="your_github_username")
+user.is_staff = True
+user.is_superuser = True
+user.save()
 ```
 
-Then you can access the Django admin interface at `/admin`.
+You can then access the Django admin interface at `/admin`.