Pass clientMode when creating a relationship marshaler (#50)

If `clientMode` is enabled on a marshaler then any `relationshipMarshaler` types that are created from it should inherit the `clientMode` setting

This allows client mode to work with struct types that use nested relationships

marshal.go

@@ -100,6 +100,7 @@ func (m *Marshaler) relationshipMarshaler(link *Link) *Marshaler {
 
 	rm.memberNameValidationMode = m.memberNameValidationMode
 	rm.link = link
+	rm.clientMode = m.clientMode
 	return rm
 }
 

marshal_test.go

@@ -650,6 +650,8 @@ func TestMarshalRelationships(t *testing.T) {
 func TestMarshalClientMode(t *testing.T) {
 	t.Parallel()
 
+	articleNoIDRelatedComplexBody := `{"data":{"type":"articles","attributes":{"title":"Bazel 101"},"relationships":{"author":{"data":{"id":"1","type":"author"},"links":{"self":"http://example.com/articles//relationships/author","related":"http://example.com/articles//author"}},"comments":{"data":[{"type":"comments"},{"type":"comments"},{"type":"comments"}],"links":{"self":"http://example.com/articles//relationships/comments","related":"http://example.com/articles//comments"}}}}}`
+
 	tests := []struct {
 		description string
 		given       any
@@ -660,6 +662,19 @@ func TestMarshalClientMode(t *testing.T) {
 			given:       &Article{ID: "", Title: "A"},
 			expect:      articleANoIDBody,
 		},
+		{
+			description: "empty primary field with relationships",
+			given: &ArticleRelated{
+				Title:  "Bazel 101",
+				Author: &authorA,
+				Comments: []*Comment{
+					{Body: "Why is Bazel so slow on my computerr?", Archived: true, Author: &authorBWithMeta},
+					{Body: "Why is Bazel so slow on my computer?", Author: &authorBWithMeta},
+					{Body: "Just use an Apple M1", Author: &authorA},
+				},
+			},
+			expect: articleNoIDRelatedComplexBody,
+		},
 	}
 
 	for i, tc := range tests {