added an operation to the dotlrn_applet service contract. the operation's name
is ChangeEventHandler and is usually implemented by change_event_handler
method in the dotlrn_applet implementation. dotLRN can throw events based on
changes to a community via the dotlrn_community::generate_change_event method.
currently the only event being thrown and handled is the 'rename' event. this
event is thrown when the name of a community is changed. the only applets that
currently listen for this event are dotlrn_fs, dotlrn_forums, and
dotlrn_calendar.
applets do not have to handle all events, only events they are interested in
handling.
we will add events on an as needed basis.
