#35 First parts of documentation for release ceremony

Signed-off-by: Sven Strittmatter <sven.strittmatter@iteratec.com>

Author: Weltraumschaf

release.md

@@ -0,0 +1,70 @@
+# Release Documentation
+
+Here we describe all the ceremonial stuff necessary to publish a Java library to Maven Central.
+
+## GPG Guide for Maven Release Signing
+
+This guide is based on [Working with PGP Signatures](https://central.sonatype.org/publish/requirements/gpg/) and [OpenPGP Best Practices](https://riseup.net/ru/security/message-security/openpgp/gpg-best-practices).
+
+### About our key
+
+Real name: `the secureCodeBox authors`
+Email: `securecodebox@iteratec.com`
+Comment: `Maven Release Signing Key`
+Fingerprint: `40AA7D29EB6DE0667D7E723ADE4725604A739BAF`
+Password: [see our password manager]
+
+### Create a new key
+
+We create a new GPG key with:
+
+```shell
+gpg --full-generate-key
+```
+
+### Import the private key
+
+Download private key from 1Password and import it locally
+
+```shell
+gpg --import private.key
+```
+
+### Export the Private Key
+
+#### For GitHub Actions
+
+```shell
+gpg --armor --export-secret-keys 40AA7D29EB6DE0667D7E723ADE4725604A739BAF
+```
+
+#### For 1Password
+
+```shell
+gpg -o private.key --export-secret-key 40AA7D29EB6DE0667D7E723ADE4725604A739BAF
+```
+
+### Expiration
+
+It is recommended to use an expiration date less than two years. We use an interval of **two years**. This means that we need to extend the expiration date every two years! 
+
+#### How to extend the expiration date?
+
+1. Download the private key file `private.key` from 1Password
+2. Import it locally:  `gpg --import private.key`
+3. Select the key : `gpg --edit-key 40AA7D29EB6DE0667D7E723ADE4725604A739BAF`
+4. Now select the subkey and set the expire date (use `2y` for two years):
+```shell
+gpg> key 1
+gpg> expire
+```
+5. Save it:
+```shell
+gpg>  save
+```
+6. Update the private key in out password manager and GitHub Secrets
+
+## TODOs
+
+- How to remember the expirationd date over time & with changing developers?
+- Do we need to import the public key in sonatype?