Add service monitoring endpoint to Apinf infrastructure

[bajiat]

All Apinf users (API consumers, API managers and Apinf administrators) need to be able to check Apinf service availability.

Definition of done

• Create REST endpoint for returning confimation, if service is up.
  • If desired, design a user interface to display the status information.

[frenchbread]

PR #358 created. Pls review, test and merge it.