Register github page website to subdomain

[rivernews]

Had to do the following. Perhaps not all of them are necessary, but if we do all these, it works, so. The github page doc on setting up github page for subdomain is pretty lack of detail or it's outdated. They didn't even mention the CNAME file.

• Route53, create CNAME for sundomain appl-tracky.shaungc.com, point to rivernews.github.io. That's right, no need to point to project repo sub path. Github will handle the routing.
• Create a file CNAME, containing the text appl-tracky.shaungc.com, place it in src/.
• To ensure the CNAME file exists in the gh-page branch root, we need to make sure it's in build/. In package.json, for the deploy (or build) script, add something like cp src/CNAME build/CNAME. Also configure 404 page. At the end, do something like this "build": "react-scripts build && cp src/CNAME build/CNAME && cp build/index.html build/404.html".
• Update package.json home page as "homepage": "https://appl-tracky.shaungc.com",.
• Run npm run deploy.
• In github repo settings, setup the custom domain to appl-tracky.shaungc.com. Also enable the "enforce HTTP".

[rivernews]

Also have to update Google Oath callback url: https://console.developers.google.com/apis/credentials/oauthclient/732988498848-vuhd6g61bnlqe372i3l5pbpnerteu6na.apps.googleusercontent.com?project=732988498848.

Frontend got error when trying to do social auth: "Not a valid origin for the client: https://appl-tracky.shaungc.com has not been whitelisted for client ID 732988498848-vuhd6g61bnlqe372i3l5pbpnerteu6na.apps.googleusercontent.com. Please go to https://console.developers.google.com/ and whitelist this origin for your project's client ID."

[rivernews]

After adding the new subdomain to backend django CORS whitelist, the error is gone now.