Now that workflows have initialize() and destroy(), a user may want to implement pluggable logic that happens in those methods.
For example, in Hydrator we want to implement plugins that always run at the end of a workflow run. There may be a plugin that sends an email, another plugin that runs a db query, another plugin that makes an http call, etc.
In order to support this, CDAP workflows need to support plugins. As far as API changes go, this amounts to extending WorkflowContext so that it implements PluginContext.