I want to be able to complete an external task asynchronously without the need for storing and maintaining state of ExternalTaskService and ExternalTask objects handed into the handler.

Proposal: Create public API that allows completion by id, like that internal-API workaround:

((ExternalTaskClientImpl) externalTaskClient).getTopicSubscriptionManager().getEngineClient().complete(<myId>);

Add the same behavior for:

• extendLock
• handleError
• handleFailure

See also https://github.com/camunda/camunda-external-task-client-java/issues/25