treewide: add license header and enable haslicense linter

Change-Id: I873a8d4082d75e8f813d8a726a41187eea7a065e
Reviewed-on: https://review.monogon.dev/c/monogon/+/3825
Tested-by: Jenkins CI
Reviewed-by: Leopold Schabel <leo@monogon.tech>
diff --git a/metropolis/test/util/curator.go b/metropolis/test/util/curator.go
index 28fa7b1..35c0b97 100644
--- a/metropolis/test/util/curator.go
+++ b/metropolis/test/util/curator.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 package util
 
 import (
diff --git a/metropolis/test/util/rpc.go b/metropolis/test/util/rpc.go
index c31c935..e2558a3 100644
--- a/metropolis/test/util/rpc.go
+++ b/metropolis/test/util/rpc.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 package util
 
 import (
diff --git a/metropolis/test/util/runners.go b/metropolis/test/util/runners.go
index 95de02a..4a8a1e9 100644
--- a/metropolis/test/util/runners.go
+++ b/metropolis/test/util/runners.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 // This file implements test helper functions that augment the way any given
 // test is run.
 package util