mysql: annotation support. Fixes #8382

Simple query editor - a text area with a Show Help section.
Validation for empty query and if the time_sec column is missing.

public/app/plugins/datasource/mysql/module.ts

@@ -9,10 +9,33 @@ class MysqlConfigCtrl {
   static templateUrl = 'partials/config.html';
 }
 
+const defaultQuery = `SELECT
+    UNIX_TIMESTAMP(<time_column>) as time_sec,
+    <title_column> as title,
+    <text_column> as text,
+    <tags_column> as tags
+  FROM <table name>
+  WHERE $__timeFilter(time_column)
+  ORDER BY <time_column> ASC
+  LIMIT 100
+  `;
+
+class MysqlAnnotationsQueryCtrl {
+  static templateUrl = 'partials/annotations.editor.html';
+
+  annotation: any;
+
+  /** @ngInject **/
+  constructor() {
+    this.annotation.rawQuery = this.annotation.rawQuery || defaultQuery;
+  }
+}
+
 export {
   MysqlDatasource,
   MysqlDatasource as Datasource,
   MysqlQueryCtrl as QueryCtrl,
   MysqlConfigCtrl as ConfigCtrl,
+  MysqlAnnotationsQueryCtrl as AnnotationsQueryCtrl,
 };