Extended functionality base class for SCM implementations that only want to handle one event system and
are consolidating on the SCM API event system. It is not strictly required to extend from this class in place of
SCM but typically implementations would need to have the functionality made available from
afterSave(SCMTriggerItem) and/or getItemActions(SCMTriggerItem). Implementations that do
not require these features can get integration with the SCM API event subsystem by implementing
Callback from the SCMTriggerItem after the SCMTriggerItem has been saved. Can be used to
register the SCMTriggerItem for a call-back hook from the backing SCM that this source is for.
Implementations are responsible for ensuring that they do not create duplicate registrations and that orphaned
registrations are removed eventually.