ActionHandler is a request scope bean responsible for handling an HTTP POST
request, or other non-idempotent web service "action" cycle. Defines the core
logic for this processing cycle.
author: Antranig Basman (antranig@caret.cam.ac.uk)
The result of this post cycle will be of interest to some other request
beans, in particular the alteration wrapper. This bean must however be
propagated lazily since it is only constructed partway through this
handler, if indeed it is a POST cycle at all.
The ARIResult resulting from this action cycle.