Adds backend hooks service so extensions can modify index data

pkg/services/hooks/hooks.go

@@ -0,0 +1,30 @@
+package hooks
+
+import (
+	"github.com/grafana/grafana/pkg/api/dtos"
+	"github.com/grafana/grafana/pkg/registry"
+)
+
+type IndexDataHook func(indexData *dtos.IndexViewData)
+
+type HooksService struct {
+	indexDataHooks []IndexDataHook
+}
+
+func init() {
+	registry.RegisterService(&HooksService{})
+}
+
+func (srv *HooksService) Init() error {
+	return nil
+}
+
+func (srv *HooksService) AddIndexDataHook(hook IndexDataHook) {
+	srv.indexDataHooks = append(srv.indexDataHooks, hook)
+}
+
+func (srv *HooksService) RunIndexDataHooks(indexData *dtos.IndexViewData) {
+	for _, hook := range srv.indexDataHooks {
+		hook(indexData)
+	}
+}