Allow white labeling loading logo (#36174) (#36386)

* Allow to whitelabeling loading logo

* Add loading_logo to documentation

* Change loading_logo to loading_logo_url

(cherry picked from commit ef05596e07)

Co-authored-by: Selene <selenepinillos@gmail.com>

pkg/api/dtos/index.go

@@ -26,6 +26,7 @@ type IndexViewData struct {
 	AppTitle                string
 	Sentry                  *setting.Sentry
 	ContentDeliveryURL      string
+	LoadingLogo             template.URL
 	// Nonce is a cryptographic identifier for use with Content Security Policy.
 	Nonce string
 }

pkg/api/index.go

@@ -461,6 +461,7 @@ func (hs *HTTPServer) setIndexViewData(c *models.ReqContext) (*dtos.IndexViewDat
 		Sentry:                  &hs.Cfg.Sentry,
 		Nonce:                   c.RequestNonce,
 		ContentDeliveryURL:      hs.Cfg.GetContentDeliveryURL(hs.License.ContentDeliveryPrefix()),
+		LoadingLogo:             "public/img/grafana_icon.svg",
 	}
 
 	if hs.Cfg.FeatureToggles["accesscontrol"] {