Expose folder UID in dashboards API response (#33991)

* expose folder UID in dashboards API response, import dashboards into folders by folder UID

* handle bad folder UID as 400 error

* 12591:Add tests for request with folderUid

* Use more descriptive error status for missing folders

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>

* return 400 when folder id is missing

* put error checking in the right place this time

* mention folderUid in the docs

* Clarify usage of folderUid and folderId when both present

Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>

* Capitalise UID

Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

* mention folder UID in the metadata for a GET response

Co-authored-by: Ida Furjesova <ida.furjesova@grafana.com>
Co-authored-by: Marcus Efraimsson <marcus.efraimsson@gmail.com>
Co-authored-by: achatterjee-grafana <70489351+achatterjee-grafana@users.noreply.github.com>

docs/sources/http_api/dashboard.md

@@ -44,6 +44,7 @@ Authorization: Bearer eyJrIjoiT0tTcG1pUlY2RnVKZTFVaDFsNFZXdE9ZWmNrMkZYbk
     "refresh": "25s"
   },
   "folderId": 0,
+  "folderUid": "l3KqBxCMz",
   "message": "Made changes to xyz",
   "overwrite": false
 }
@@ -55,6 +56,7 @@ JSON Body schema:
 - **dashboard.id** – id = null to create a new dashboard.
 - **dashboard.uid** – Optional unique identifier when creating a dashboard. uid = null will generate a new uid.
 - **folderId** – The id of the folder to save the dashboard in.
+- **folderUid** – The UID of the folder to save the dashboard in. Overrides the `folderId`.
 - **overwrite** – Set to true if you want to overwrite existing dashboard with newer version, same dashboard title in folder or same dashboard uid.
 - **message** - Set a commit message for the version history.
 - **refresh** - Set the dashboard refresh interval. If this is lower than [the minimum refresh interval]({{< relref "../administration/configuration.md#min_refresh_interval">}}), then Grafana will ignore it and will enforce the minimum refresh interval.
@@ -268,7 +270,7 @@ In case of title already exists the `status` property will be `name-exists`.
 
 `GET /api/dashboards/uid/:uid`
 
-Will return the dashboard given the dashboard unique identifier (uid).
+Will return the dashboard given the dashboard unique identifier (uid). Information about the unique identifier of a folder containing the requested dashboard might be found in the metadata.
 
 **Example Request**:
 
@@ -298,6 +300,8 @@ Content-Type: application/json
   "meta": {
     "isStarred": false,
     "url": "/d/cIBgcSjkk/production-overview",
+    "folderId": 2,
+    "folderUid": "l3KqBxCMz",
     "slug": "production-overview" //deprecated in Grafana v5.0
   }
 }