Clarify Github Integration Instructions

Hi again,

Finally got the Github integration working after 24 hours. I'd like to document extra details that were missed in the installation steps here.

Take a look at [Plane's guide](https://developers.plane.so/self-hosting/govern/integrations/github) for a better example of step-by-step examples.

Firstly, I don't know if it was a necessary step, but it might have been – we had to configure Github OAuth through an OAuth app first. Here there's the issue of multiple environment variables with the same name (GITHUB_CLIENT_SECRET), so ensure to name those differently (i.e. GITHUB_APP_CLIENT_SECRET for the integration app), and adjust the `compose.yml` file so that `account` container points to the OAuth app, and `github` container points to the Integration App.

I had to ensure the callback URLs are properly configured as `https:///_accounts/auth/github/callback` - That meant checking the `.huly.nginx` redirect for `account`, as well as the URLs in the `front` and `account` containers in `compose.yml`. I can't remember if it was configured like this by default, so I'm leaving this here just in case.

Then, when you go about creating a Github app, **you shouldn't miss these steps**:

### Make sure to check:

- **Expire user authorization tokens** (for security)
- **Request user authorization (OAuth) during installation**
- **Redirect on update**

You can configure these options on an already-existing/installed app, as we did. However, you'll have to **uninstall it first** by going through "My Apps", and then re-install it by going through the "Integrations" menu in Huly.

Thankfully we got it working in the end. My advice is, create a full step-by-step guide where you create the app on behalf of an organisation, and configure a fresh Huly instance to link to it. Wish you guys all the best and looking forward to using Huly 👍