Dashboard migration: Implement v2 to v0 conversions (#114812)

* Update docs

* Remove 406 response since now it is converted

* fix linter

---------

Co-authored-by: Stephanie Hingtgen <stephanie.hingtgen@grafana.com>

pkg/api/dashboard.go

@@ -96,12 +96,6 @@ func (hs *HTTPServer) GetDashboard(c *contextmodel.ReqContext) response.Response
 		return rsp
 	}
 
-	// v2 is not supported in /api
-	if strings.HasPrefix(dash.APIVersion, "v2") {
-		url := fmt.Sprintf("/apis/dashboard.grafana.app/%s/namespaces/%s/dashboards/%s", dash.APIVersion, hs.namespacer(c.GetOrgID()), dash.UID)
-		return response.Error(http.StatusNotAcceptable, "dashboard api version not supported, use "+url+" instead", nil)
-	}
-
 	var (
 		publicDashboardEnabled = false
 		err                    error