Create Annotation.

Creates an annotation in the Grafana database. The dashboardId and panelId fields are optional. If they are not specified then an organization annotation is created and can be queried in any dashboard that adds the Grafana annotations data source. When creating a region annotation include the timeEnd property. The format for time and timeEnd should be epoch numbers in millisecond resolution. The response for this HTTP request is slightly different in versions prior to v6.4. In prior versions you would also get an endId if you where creating a region. But in 6.4 regions are represented using a single event with time and timeEnd properties.