Send an edition.updated payload to LTD Events
Send an edition.updated payload to LTD Events

This happens at the end of the edition rebuild task. The content of the
payload matches the schema defined by LTD Events
(https://github.com/lsst-sqre/ltd-events).

This is designed so that a failure of the webhook post won't destabilize
the edition rebuild in general.

lsst-sqre/ltd-keeper,lsst-sqre/ltd-keeper