docs: add reuse docu

docs/dev.md

@@ -0,0 +1,46 @@
+<!--
+SPDX-FileCopyrightText: 2025 Deutsche Telekom IT GmbH
+
+SPDX-License-Identifier: CC-BY-4.0
+-->
+
+# Developer Documentation <!-- omit from toc -->
+
+- [Using `reuse` for license handling](#using-reuse-for-license-handling)
+  - [Install](#install)
+  - [CLI Usage](#cli-usage)
+  - [`REUSE.toml`](#reusetoml)
+
+## Using `reuse` for license handling
+
+`reuse` is a [cli tool](https://reuse.readthedocs.io/en/latest/index.html) to handle licenses with [SPDX standard](https://spdx.dev/use/overview/) in a repository.
+
+How `reuse` is setup and used is explained in the [Telekom Org documentation](https://telekom.github.io/reuse-template/using-the-template/setup-reuse).
+
+For details about license handling with `reuse` checkout this [page](https://telekom.github.io/reuse-template/using-the-template/setup-license).
+
+### Install
+
+Install `reuse` following the [official instructions](https://reuse.readthedocs.io/en/latest/readme.html#install).
+
+`reuse` is embedded as a pre-commit hook. Install `pre-commit install` to use it. The hook is checking the repository to stay compliant in terms of licenses.
+
+### CLI Usage
+
+> `reuse lint`
+
+Verify the compliance of the repository.
+
+> `reuse annotate -c "Deutsche Telekom IT GmbH" -l "Apache-2.0" --recursive --skip-existing --fallback-dot-license <PATH-TO-FILE/DIR>`
+
+Annotate a file or directory with the `Apache-2.0` SPDX license header. In case the tool is not able to append a header, a `.license` file is created.
+
+> `reuse annotate -c "Deutsche Telekom IT GmbH" -l "CC-BY-4.0" --recursive --skip-existing --fallback-dot-license ./docs/*.md`
+
+Use the `CC-BY-4.0` SPDX license header for documentation (eg. `.md`) files.
+
+### `REUSE.toml`
+
+In case a license header is not suitable for a file or directory (eg. auto-generated files) the `REUSE.toml` configuration file can be used.
+
+Add the file path to the `REUSE.toml` or create a new `[[annotations]]` section (see `./REUSE.toml` for an example).