||An interface representing a message handler.
||Well-behaved MessageHandler implementations should use as much as possible
this interface to create approprate entities.
||Message handlers should report here what they are doing
Depending on the context in which handlers are run (either normal production run as from a
scheduled service or in a test mode - a dry run - from UI) this information can be transparently
routed to appropriate place.
||This is extension to MessageHandlerErrorCollector interface for
with a few reporting methods around Messages.
||This call is going to be moved away from API into JIRA Mail Plugin.
||A set of User-related util methods which can be useful while processing Message objects.