The abort() method calls loseConnection() which tries to shutdown the
TLS connection cleanly. We now call abortConnection() directly which
should promptly close both the TLS connection and the underlying TCP
connection.
I also added some TODO markers to consider cancelling the old previous
timeout rather than checking time.time(). But given how urgently we want
to get this code released I'd rather leave the existing code with the
duplicate timeouts and the time.time() check.
Add url_preview_ip_range_blacklist to let admins specify internal IP ranges that must not be spidered.
Add url_preview_url_blacklist to let admins specify URL patterns that must not be spidered.
Implement a custom SpiderEndpoint and associated support classes to implement url_preview_ip_range_blacklist
Add commentary and generally address PR feedback
Mark Haines