Return max depth folder reached instead of a generic error (#99804)

* Return max depth folder reached instead of a generic error

* Unit test error function

* Lint

* Update pkg/api/apierrors/folder.go

Co-authored-by: Jean-Philippe Quéméner <JohnnyQQQQ@users.noreply.github.com>

---------

Co-authored-by: Jean-Philippe Quéméner <JohnnyQQQQ@users.noreply.github.com>

pkg/api/apierrors/folder.go

@@ -10,6 +10,7 @@ import (
 
 	"github.com/grafana/grafana/pkg/api/response"
 	"github.com/grafana/grafana/pkg/services/dashboards"
+	"github.com/grafana/grafana/pkg/services/folder"
 	"github.com/grafana/grafana/pkg/util"
 )
 
@@ -43,6 +44,11 @@ func ToFolderErrorResponse(err error) response.Response {
 		return response.JSON(http.StatusPreconditionFailed, util.DynMap{"status": "version-mismatch", "message": dashboards.ErrFolderVersionMismatch.Error()})
 	}
 
+	// folder errors are wrapped in an error util, so this is the only way of comparing errors
+	if err.Error() == folder.ErrMaximumDepthReached.Error() {
+		return response.JSON(http.StatusBadRequest, util.DynMap{"messageId": "folder.maximum-depth-reached", "message": "Maximum nested folder depth reached"})
+	}
+
 	return response.ErrOrFallback(http.StatusInternalServerError, "Folder API error", err)
 }