REST: Fix PATCH method (kubeflow#151)

* update goverter to 1.4.1

As that fixed a nil assignment override[1][2] which prevented us from
emulating copy constructors[3].
The update also allows us to use generics.

[1]: jmattheis/goverter#146 (comment)
[2]: jmattheis/goverter#97
[3]: jmattheis/goverter#147

Signed-off-by: Isabella Basso do Amaral <idoamara@redhat.com>
Signed-off-by: Isabella do Amaral <idoamara@redhat.com>

* simplify converter utils using generics

Signed-off-by: Isabella do Amaral <idoamara@redhat.com>

* server: update existing objects on PATCH

Signed-off-by: Isabella do Amaral <idoamara@redhat.com>

---------

Signed-off-by: Isabella Basso do Amaral <idoamara@redhat.com>
Signed-off-by: Isabella do Amaral <idoamara@redhat.com>

Makefile

@@ -130,7 +130,7 @@ bin/golangci-lint:
 
 GOVERTER ?= ${PROJECT_BIN}/goverter
 bin/goverter:
-	GOBIN=$(PROJECT_PATH)/bin ${GO} install github.com/jmattheis/goverter/cmd/goverter@v1.1.1
+	GOBIN=$(PROJECT_PATH)/bin ${GO} install github.com/jmattheis/goverter/cmd/goverter@v1.4.1
 
 OPENAPI_GENERATOR ?= ${PROJECT_BIN}/openapi-generator-cli
 NPM ?= "$(shell which npm)"