The current behavior of BaseDelegateExecution#getBusinessKey  is rather useless because there is no value in cases when the method returns null. Users often confuse this with #getProcessBusinessKey.
- #getBusinessKey works like #getProcessBusinessKey
- it could make sense to mention this in the update guide
- The motivation for the introduction of #getProcessBusinessKey (see ) does not make much sense because persistence does not require an API method.