Additional fields on SecurityIdentity

The following useful properties could be added to SecurityIdentity:

• Identity creation time (the time when the identity itself is created, whether by login or by run-as)
• Authentication information, including:
  • Login timestamp (the time of the original authentication)
  • Login mechanism & kind (SASL/HTTP/TLS etc.)
  • Login protocol (HTTP/Remoting/etc.) incl. enclosing TLS information if any
• Authentication identity information, including:
  • Original authentication name
  • Authentication forwarding credential(s)
• Connection circumstances:
  • Peer and local address
  • Current invocation protocol