chore(doc): add documentation of release process (#1840)

relates to STACKITTPR-200

Author: rubenhoenle

README.md

@@ -228,6 +228,10 @@ If you encounter any issues or have suggestions for improvements, please open an
 
 Your contribution is welcome! For more details on how to contribute, refer to our [Contribution Guide](./CONTRIBUTION.md).
 
+## Release creation
+
+See the [release documentation](./RELEASE.md) for further information.
+
 ## License
 
 Apache 2.0

RELEASE.md

@@ -0,0 +1,42 @@
+# Release
+
+## Release cycle
+
+A release of the whole SDK should be created at least every 2 weeks. 
+
+## Release creation
+
+### Single service
+
+The SDK is split into all the different STACKIT [services](https://github.com/stackitcloud/stackit-sdk-go/tree/main/services), each of them having their own version numbers.
+
+**Checklist before releasing a single service**
+
+- [ ] Changelog entries were added to the `CHANGELOG.md` in the root directory of the repository (see [here](https://github.com/stackitcloud/stackit-sdk-go/blob/f1e375a38064f798821d22a951bc74ca8a9c8845/CHANGELOG.md))
+- [ ] Changelog entries were added to the `CHANGELOG.md` file of the service to be released (see e.g. [here](https://github.com/stackitcloud/stackit-sdk-go/blob/f1e375a38064f798821d22a951bc74ca8a9c8845/services/dns/CHANGELOG.md))
+
+**Releasing a single service**
+
+1. Check out latest main branch on your machine
+2. Create git tag: `git tag services/<SERVICE-NAME>/vX.X.X`
+    - E.g. for the `sqlserverflex` service version `v1.0.1` the git tag would be named `services/sqlserverflex/v1.0.1`
+3. Push the git tag: `git push origin --tags`
+
+### Whole SDK
+
+**Checklist before releasing the whole SDK**
+
+- [ ] Date was set/updated in the `CHANGELOG.md` file in the root directory of the repository (see [here](https://github.com/stackitcloud/stackit-sdk-go/blob/f1e375a38064f798821d22a951bc74ca8a9c8845/CHANGELOG.md))
+
+**Releasing the whole SDK**
+
+> [!IMPORTANT]
+> Consider informing / syncing with the team before creating a new release.
+
+1. Check out latest main branch on your machine
+2. Create git tag: `git tag release-YYYY-MM-DD`
+3. Push the git tag: `git push origin --tags`
+4. Copy the changelog entries for the new release from the `CHANGELOG.md` file in the root directory of the repository (see [here](https://github.com/stackitcloud/stackit-sdk-go/blob/f1e375a38064f798821d22a951bc74ca8a9c8845/CHANGELOG.md)) to your clipboard.
+5. Go to the [releases page](https://github.com/stackitcloud/stackit-sdk-go/releases) on GitHub and create a new release. Select the git tag you just created.
+6. Before creating the GitHub release, add the *Highlights* heading at the top of the markdown description and paste the changelog entries from your clipboard (see [previous releases](https://github.com/stackitcloud/stackit-sdk-go/releases/tag/release-2025-03-27) to see what it should look like). Then create and publish the GitHub release.
+