docs(http): adds info about mass pausing alerts

docs/sources/http_api/admin.md

@@ -275,3 +275,20 @@ Change password for specific user
     Content-Type: application/json
 
     {message: "User deleted"}
+
+## Pause all alerts
+
+`DELETE /api/admin/pause-all-alerts`
+
+**Example Request**:
+
+    DELETE /api/admin/pause-all-alerts HTTP/1.1
+    Accept: application/json
+    Content-Type: application/json
+
+**Example Response**:
+
+    HTTP/1.1 200
+    Content-Type: application/json
+
+    {state: "new state", message: "alerts pause/un paused", "alertsAffected": 100}