refactor: add link to migration guide (planning#1684))

CHANGELOG.md

@@ -31,6 +31,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/).
 - New internal core``KeyGenerator`` to generate X509 test certificates, RSA-KeyPairs and JWKs (planning#664)
 
 ### Changed
+
+For further details on the changes related to this update please have a look a the [Update Guide](docs/update-guide.md)
+
 - Updated schemas:
   - Metadata-schema 1.2.0
   - SET-schema 1.2.1