This change introduces more readable and useful output by adding the
certificate expiration to the human readable string. The response time
is now formatted too.
- C2S and S2S are quite similar, only stream initialization is a bit different
- rename methods to make this clear
- remove branching for client and server
- use one ContentHandler for client and server
- add more debug logging
- always return all metrics
- add method handle_xmpp_stanza that uses select to check socket for available
data and feed the XML parser
- use defusedxml for more robust XML parsing
