DF Reference to object Service: wrong Key for external source

[StefanAbel-OTOBO]

When trying to create a Dynamic Field Reference to object Service, you can select a Key for external source as for other Reference Dynamic Fields. For referenced objects it makes sense to have options sucht as Login or Email, but for Service those options don't make sense.

Tested on OTOBO 11.0.16 with ServiceCatalog 11.0.6

[stefanhaerter]

Transferred because the Service reference dynamic field driver is located in package ITSMCore.