Appmanager should cover target device - (Appstore) user mapping

[rohoet]

Currently, in order to select a target device in the App Store for some user, the username must be mentioned within the description field of a target in Eclipse Hawkbit.

It would be nice to automate the process such that

• admin is initially entered in the description field of a new registered target
• the app manager optionally reads / takes credentials wich are validated through a keycloak server communication in order to allow direct and distinct initial target device - user mapping