chore add licenses

Makefile

+## Copyright 2022 schukai GmbH. All rights reserved.
+## Use of this source code is governed by a AGPL-3.0
+## license that can be found in the LICENSE file.
+
 PROJECT_ROOT:=$(dir $(realpath $(lastword $(MAKEFILE_LIST))))
 THIS_MAKEFILE:=$(word $(words $(MAKEFILE_LIST)),$(MAKEFILE_LIST))
 THIS_MAKEFILE_PATH:=$(PROJECT_ROOT)$(THIS_MAKEFILE) 
@@ -137,5 +141,16 @@ endif
 fetch-licenses:
 	go-licenses save $(GO_CURRENT_MODULE) --ignore gitlab.schukai.com --force --save_path $(PROJECT_ROOT)licenses/ ; cd -
 
+# https://spdx.github.io/spdx-spec/v2.3/SPDX-license-list/
+ADDLICENSE_BIN ?= addlicense
+ifeq ($(shell command -v $(ADDLICENSE_BIN) 2> /dev/null),)
+	$(shell go install github.com/google/addlicense@latest)
+	EXECUTABLES = $(EXECUTABLES:-) $(ADDLICENSE_BIN);
+endif
+
+.PHONY: add-licenses
+## Add license headers to all go files
+add-licenses:
+	addlicense -c "schukai GmbH" -s -l "AGPL-3.0-or-later" ./*.go
 
 

api.go

+// Copyright 2022 schukai GmbH
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
 package negotiation
 
 import (

api_test.go

+// Copyright 2022 schukai GmbH
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
 package negotiation
 
 import (

header.go

+// Copyright 2022 schukai GmbH
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
 package negotiation
 
 const (

parser.go

+// Copyright 2022 schukai GmbH
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
 package negotiation
 
 import (

parser_test.go

+// Copyright 2022 schukai GmbH
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
 package negotiation
 
 import (

spec.go

+// Copyright 2022 schukai GmbH
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
 package negotiation
 
 import "strings"

spec_test.go

+// Copyright 2022 schukai GmbH
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
 package negotiation
 
 import (