chore(license): state copyright and license in all py-files

src/main.py

+# SPDX-FileCopyrightText: 2022 Georg-August-Universität Göttingen
+#
+# SPDX-License-Identifier: CC0-1.0
+
 """Configure and start the WSGI DAV Server."""
 import logging
 import os

src/repdav/config.py

+# SPDX-FileCopyrightText: 2022 Georg-August-Universität Göttingen
+#
+# SPDX-License-Identifier: CC0-1.0
+
 import os
 
 from .errors import EnvNotSetError

src/repdav/errors.py

+# SPDX-FileCopyrightText: 2022 Georg-August-Universität Göttingen
+#
+# SPDX-License-Identifier: CC0-1.0
+
 """Custom error classes
 """
 import logging

src/repdav/textgrid_dav_provider.py

+# SPDX-FileCopyrightText: 2022 Georg-August-Universität Göttingen
+#
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
 """The DAV resource provider and its resources.
 """
 import io

src/repdav/textgrid_domain_controller.py

+# SPDX-FileCopyrightText: 2022 Georg-August-Universität Göttingen
+#
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
 import logging
 from wsgidav.dc.base_dc import BaseDomainController
 # see https://github.com/mar10/wsgidav/blob/master/wsgidav/dc/base_dc.py

src/repdav/textgrid_named_dav_provider.py

+# SPDX-FileCopyrightText: 2022 Georg-August-Universität Göttingen
+#
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
 import logging
 from pprint import pformat