AuthRestHandler: support login by API key via REST-UI
AuthRestHandler: support login by API key via REST-UI

The AuthRestHandler now accepts ApiKeyCredentials specified by entry
"key" in the login message.

Signed-off-by: Jan Viktorin <3eab6ac54c005c4408f608556a6663b7f2abede7@fit.vutbr.cz>

BeeeOn/server,BeeeOn/server,BeeeOn/server,BeeeOn/server