Fix empty resources spec field failing schema validation (#1589)

In Go, when a struct field is not set, it becomes a struct with
default values for all fields. These default values are included
during serialization. This causes issues with schema validation
where optional fields cannot be omitted because default values
are considered invalid.

This patch addresses this issue for `Resources` fields on several
types by using a pointer value.

pkg/cluster/cluster_test.go

@@ -60,7 +60,7 @@ func TestStatefulSetAnnotations(t *testing.T) {
 	testName := "CheckStatefulsetAnnotations"
 	spec := acidv1.PostgresSpec{
 		TeamID: "myapp", NumberOfInstances: 1,
-		Resources: acidv1.Resources{
+		Resources: &acidv1.Resources{
 			ResourceRequests: acidv1.ResourceDescription{CPU: "1", Memory: "10"},
 			ResourceLimits:   acidv1.ResourceDescription{CPU: "1", Memory: "10"},
 		},