Get Backend API base URL from environment variable - using runtime config for NextJS

[shahariaazam]

When running in docker, we should be able to set the backend api endpoint (API_BASE_URL) as an environment variable. So the same docker image can be used for various deployment.

Currently the frontend will by default set the API base url to http://localhost:8080

Reference: vercel/next.js#44628

[shahariaazam]

I think there is no straight-forward way due to the nature and limitation by NextJS. We wanted to do some experiment here.