Add conflict handling for managed network elements

api/go/gosdn/networkelement/networkelement.pb.go

api/go/gosdn/topology/link.pb.go

api/go/gosdn/topology/node.pb.go

api/go/gosdn/topology/port.pb.go

api/go/gosdn/topology/route.pb.go

api/go/gosdn/topology/routingTable.pb.go

api/openapiv2/gosdn_northbound.swagger.json

api/proto/buf.lock

api/proto/gosdn/networkelement/networkelement.proto

api/proto/gosdn/topology/link.proto

api/proto/gosdn/topology/node.proto

api/proto/gosdn/topology/port.proto

api/proto/gosdn/topology/route.proto

api/proto/gosdn/topology/routingTable.proto

controller/api/initialise_test.go

controller/interfaces/networkelement/networkElement.go

controller/mocks/Device.go

controller/mocks/NetworkElement.go

controller/mocks/Service.go

controller/mocks/User.go