API: return resource ID when deleting datasource with UID and library element (#41342)

* API: return resource ID when deleting datasource and library element

* keep status codes consistent

* fix element ID

* add test

* improve response struct

* update endpoints documentation

* LibraryElementIDResponse -> DeleteLibraryElementResponse

docs/sources/http_api/library_element.md

@@ -442,7 +442,8 @@ HTTP/1.1 200
 Content-Type: application/json
 
 {
-    "message": "Library element deleted"
+    "message": "Library element deleted",
+    "id": 28
 }
 ```