Added PATCH verb end point for annotation op

Added new PATCH verb annotation endpoint

Removed unwanted fmt

Added test cases for PATCH verb annotation endpoint

Fixed formatting issue

Check arr len before proceeding

Updated doc to include PATCH verb annotation endpt

pkg/api/annotations.go

@@ -210,6 +210,65 @@ func UpdateAnnotation(c *m.ReqContext, cmd dtos.UpdateAnnotationsCmd) Response {
 	return Success("Annotation updated")
 }
 
+func PatchAnnotation(c *m.ReqContext, cmd dtos.PatchAnnotationsCmd) Response {
+	annotationID := c.ParamsInt64(":annotationId")
+
+	repo := annotations.GetRepository()
+
+	if resp := canSave(c, repo, annotationID); resp != nil {
+		return resp
+	}
+
+	items, err := repo.Find(&annotations.ItemQuery{AnnotationId: annotationID, OrgId: c.OrgId})
+
+	if err != nil || len(items) == 0 {
+		return Error(500, "Could not find annotation to update", err)
+	}
+
+	existing := annotations.Item{
+		OrgId:    c.OrgId,
+		UserId:   c.UserId,
+		Id:       annotationID,
+		Epoch:    items[0].Time,
+		Text:     items[0].Text,
+		Tags:     items[0].Tags,
+		RegionId: items[0].RegionId,
+	}
+
+	if cmd.Tags != nil {
+		existing.Tags = cmd.Tags
+	}
+
+	if cmd.Text != "" && cmd.Text != existing.Text {
+		existing.Text = cmd.Text
+	}
+
+	if cmd.Time > 0 && cmd.Time != existing.Epoch {
+		existing.Epoch = cmd.Time
+	}
+
+	if err := repo.Update(&existing); err != nil {
+		return Error(500, "Failed to update annotation", err)
+	}
+
+	// Update region end time if provided
+	if existing.RegionId != 0 && cmd.TimeEnd > 0 {
+		itemRight := existing
+		itemRight.RegionId = existing.Id
+		itemRight.Epoch = cmd.TimeEnd
+
+		// We don't know id of region right event, so set it to 0 and find then using query like
+		// ... WHERE region_id = <item.RegionId> AND id != <item.RegionId> ...
+		itemRight.Id = 0
+
+		if err := repo.Update(&itemRight); err != nil {
+			return Error(500, "Failed to update annotation for region end time", err)
+		}
+	}
+
+	return Success("Annotation patched")
+}
+
 func DeleteAnnotations(c *m.ReqContext, cmd dtos.DeleteAnnotationsCmd) Response {
 	repo := annotations.GetRepository()