Converts a region name, UTC, or a fixed offset to ZoneId

All 3 scenarios hold

Region zones carry daylight-saving rules; UTC and plain offsets are fixed.

expected outcome broken scenario
ScenarioInput valueParameter type?ZoneId fixed offset?
Region zoneEurope/Berlinjava.time.ZoneIdfalse
UTCUTCjava.time.ZoneIdtrue
Plain offset+02:00java.time.ZoneIdtrue