Access control: Build navigation links with access control (#33024)

* Build nav links with access control

* Break up getNavTree (reduce cyclomatic complexity)

* Fix tests

* Use only ActionUsersRead permissions

* Remove unused permissions definitions

* Chore: remove unused fallbacks

* Fix linter error

pkg/services/accesscontrol/accesscontrol.go

@@ -17,6 +17,26 @@ type AccessControl interface {
 	IsDisabled() bool
 }
 
+func HasAccess(ac AccessControl, c *models.ReqContext) func(fallback func(*models.ReqContext) bool, permission string, scopes ...string) bool {
+	return func(fallback func(*models.ReqContext) bool, permission string, scopes ...string) bool {
+		if ac.IsDisabled() {
+			return fallback(c)
+		}
+
+		hasAccess, err := ac.Evaluate(c.Req.Context(), c.SignedInUser, permission, scopes...)
+		if err != nil {
+			c.Logger.Error("Error from access control system", "error", err)
+			return false
+		}
+
+		return hasAccess
+	}
+}
+
+var ReqGrafanaAdmin = func(c *models.ReqContext) bool {
+	return c.IsGrafanaAdmin
+}
+
 func BuildPermissionsMap(permissions []*Permission) map[string]map[string]string {
 	permissionsMap := make(map[string]map[string]string)
 	for _, p := range permissions {