Adjust permissions of the www-pipeline and add some basic documentation (#945)

* Add basic publishing documentation
* Grand write permission to next.fritz2.dev publishing pipeline
* Finalize docu

Author: haukesomm

.github/workflows/libs.yml

@@ -8,6 +8,8 @@ on:
 jobs:
   publish:
     runs-on: ubuntu-latest
+    permissions:
+      contents: write
     steps:
     - uses: actions/checkout@v4
 

doc/PUBLISHING.md

@@ -0,0 +1,57 @@
+# Publishing
+
+fritz2 artifacts are published to [Maven Central](https://search.maven.org/search?q=g:dev.fritz2).
+
+In order to authenticate, the GitHub actions workflows of this project use a bunch of secrets that are stored
+as GitHub repository secrets. Below you can find a guide on how to obtain these secrets.
+
+## Overview of Required Secrets
+
+| Secret Name              | Description                                                           |
+|--------------------------|-----------------------------------------------------------------------|
+| `OSSRH_USERNAME`         | Your Sonatype token username.                                         |
+| `OSSRH_PASSWORD`         | Your Sonatype token password / personal access token.                 |
+| `GPG_SIGNING_KEY`        | Your GPG private key for signing artifacts.                           |
+| `GPG_SIGNING_PASSPHRASE` | The passphrase for your GPG private key.                              |
+| `FRITZ2_WEB_TOKEN`       | Token for deploying the release build of the website to GitHub Pages. |
+
+> [!NOTE]
+> Note: The `snapshot`-version of the website is hosted via GitHub pages in _this_ repository, so no additional secrets
+> are needed for that.  
+> The `release`-version of the website is hosted via GitHub pages in the
+> [fritz2-web](https://github.com/jwstegemann/fritz2-web) repository, so an additional secret (`FRITZ2_WEB_TOKEN`) is
+> needed for that. It is a personal access token with write access to the `fritz2-web` repository.
+
+## Obtaining Credentials
+
+### 1. `OSSRH_USERNAME`, `OSSRH_PASSWORD`
+
+Log in to your Sonatype account and generate a personal access token.
+You will receive a username and password/token to use for publishing.
+
+### 2. `GPG_SIGNING_KEY`, `GPG_SIGNING_PASSPHRASE`
+
+Maven Central requires the submitted artifacts to be signed with GPG.
+Below are instructions on how to create a GPG key pair and export the necessary information:
+
+1. **Generate a GPG Key Pair:**
+   ```sh
+   gpg --full-generate-key
+   ```
+    - Type: RSA and RSA (or ECC), at least 4096 bits recommended.
+    - Choose a passphrase you’ll remember (`GPG_SIGNING_PASSPHRASE`).
+
+2. **Export your GPG Private Key (for signing):**
+   ```sh
+   gpg --armor --export-secret-keys YOUR_KEY_ID
+   ```
+    - Replace `YOUR_KEY_ID` with your GPG key’s ID (`gpg --list-secret-keys`).
+    - Copy the entire output (including `-----BEGIN PGP PRIVATE KEY BLOCK-----`).
+    - This will be the value for `GPG_SIGNING_KEY`.
+
+3. **Export your GPG Public Key (upload to key server):**
+   ```sh
+   gpg --armor --export YOUR_KEY_ID
+   ```
+    - Upload this public key to a key server (e.g., [keyserver.ubuntu.com](https://keyserver.ubuntu.com/)) so Maven
+      Central can verify your signature.