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/cloud/bmaas/bmdb/webug/webug.go b/cloud/bmaas/bmdb/webug/webug.go
index f4d3e4a..137a0fd 100644
--- a/cloud/bmaas/bmdb/webug/webug.go
+++ b/cloud/bmaas/bmdb/webug/webug.go
@@ -1,3 +1,6 @@
+// Copyright The Monogon Project Authors.
+// SPDX-License-Identifier: Apache-2.0
+
 // Package webug implements a web-based debug/troubleshooting/introspection
 // system for the BMDB. It's optimized for use by developers and trained
 // operators, prioritizing information density, fast navigation and heavy