NXP-16068 : Core Extended Field : External Reference Resolver : Remove generics from Resolver to enable multi types resolving (ex: NuxeoPrincipal + NuxeoGroup)
NXP-16068 : Core Extended Field : External Reference Resolver : ensure custom field validation works
NXP-16068 : Core Extended Field : External Reference Resolver : test reference on list and complex fields
NXP-16068 : Core Extended Field : Principal reference fields