Updater service

[tiero]

Add a simple service that takes care to poll the versions.json as the source of truth for the latest version of the services to be "stable".

The service should

• expose an endpoint to give the currently running version and the new ones with a newer version for each service.
• expose an endpoint to trigger a docker pull (and also restart?) on the latest images.

Optionally we can pass an AUTO_UPDATE=all|patch|minor|major env var to automatically update to the latest version based on SemVer (it can be exported by the installer script of prem-box after asking user)

[casperdcl]

alternative: https://github.com/premAI-io/prem-app/pull/458