Added license header to files (grafana#67)

Signed-off-by: Marco Pracucci <[email protected]>

Author: pracucci

metrics/user_registries.go

@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+// Provenance-includes-location: https://github.com/cortexproject/cortex/blob/master/pkg/util/metrics_helper.go
+// Provenance-includes-license: Apache-2.0
+// Provenance-includes-copyright: The Cortex Authors.
+
 package util
 
 import (

metrics/user_registries_test.go

@@ -1,3 +1,8 @@
+// SPDX-License-Identifier: AGPL-3.0-only
+// Provenance-includes-location: https://github.com/cortexproject/cortex/blob/master/pkg/util/metrics_helper_test.go
+// Provenance-includes-license: Apache-2.0
+// Provenance-includes-copyright: The Cortex Authors.
+
 package util
 
 import (