Refactor config "api" keys
The configuration of API related keys is very confusing. The path is always the same, but host/port have three different meanings that need to be supported by three different keys:
- to use by nomad client
- to return for external use
- to access the API via the internal server side network between different app container
Another thing is GUI vs API (which makes a difference in dev mode).
Similar internal vs external distinction is necessary for files (inside container, outside container).