CUWO messages API

The CUWO messages API is based on the HTML5 Channel Messaging API and provides the controller and workflow with the means to communicate with each other.

There are different types of messages being passed between the controller and workflow. They can be roughly split into lifecycle messages, operation messages, and generic messages.

Note that due to technical limitations, the channel only support communication via plain strings. Thus, the sending side must JSON-stringify any of the message objects before posting them and the receiving side must JSON-parse them on receipt and before handling them further.