The progress tracker API lets you model a tree of steps, along the same structure as protocols and subprotocols. Each step has an (optionally changing) label, and thus progress trackers can be arranged in a tree. Updates to the progress at each level flow up the tree via an RxJava observable (I guess we will use this more in future).
A simple console renderer is provided that uses ANSI escapes and Emoji to show animated progress through a protocol.
The trader demo is enhanced to use this framework, when run outside of Gradle.
It uses Artemis (an embeddable MQ broker) and can run in either a 'serving' mode, in which case it will sit around waiting to sell fake commercial paper assets, or a 'buying' mode in which case it will connect to a specified serving node and run the two party trade protocol.
Most services are either mocked out or too trivial to be useful at this point. They will be fleshed out in the future.
Quasar is a more modern, better maintained and more powerful framework. The main improvement is that this lets us avoid the ClassLoader tricks that JavaFlow was requiring, by using an agent. This introduces a requirement to mark methods that might be on a suspended stack as @Suspendable, but means that code interops cleanly. In Java 9 it is hoped that the marking requirement may even go away entirely.
