fix: return id from api when creating new annotation/graphite annotation, fixes #9798

When creating a region annotation the response will include both
id (region start id) and endId (region end id), if not only id.

pkg/services/sqlstore/annotation_test.go

@@ -37,16 +37,18 @@ func TestAnnotations(t *testing.T) {
 		repo := SqlAnnotationRepo{}
 
 		Convey("Can save annotation", func() {
-			err := repo.Save(&annotations.Item{
+			annotation := &annotations.Item{
 				OrgId:       1,
 				UserId:      1,
 				DashboardId: 1,
 				Text:        "hello",
 				Epoch:       10,
 				Tags:        []string{"outage", "error", "type:outage", "server:server-1"},
-			})
+			}
+			err := repo.Save(annotation)
 
 			So(err, ShouldBeNil)
+			So(annotation.Id, ShouldBeGreaterThan, 0)
 
 			Convey("Can query for annotation", func() {
 				items, err := repo.Find(&annotations.ItemQuery{