lock on externalId when creating new users
lock on externalId when creating new users

simong/Hilary,stuartf/Hilary,ExC0d3/Hilary,Orodan/Hilary,jfederico/Hilary,nicolaasmatthijs/Hilary,mrvisser/Hilary,timdegroote/Hilary,timdegroote/Hilary,Orodan/Hilary,simong/Hilary,ExC0d3/Hilary,nicolaasmatthijs/Hilary,mrvisser/Hilary,jfederico/Hilary,stuartf/Hilary