Continues on PLANNER-1471

Current status of the default, non-configured behaviour:

• We hardcode localhost:8080 so when the frontend in development runs on localhost:3000, it just works.

Proposal A)

• By default, the frontend must use the host, port and context root of where it got the js file
  • So only if those properties are not overridden that local env file.
  • So the frontend should not hardcode localhost:8080/, unless the host.equals("localhost")

Proposal B)

• Also read about CORS - https://spring.io/guides/gs/rest-service-cors/