global: session 2.0

• Upgrades session serialization to LZMA.

• BETTER Implements session signing. This avoids cache request for invalid sessions and reduces the DDoS attack surface.

• BETTER Removes IP address storage+checks. This avoids data privacy issues and enables users with multiple connections (e.g. WIFI+LTE, multiple WIFI connections on trains+stations) to stay signed in.

• INCOMPATIBLE Drops all active sessions during upgrade. Might result in log entries about non-restorable sessions.

• AMENDS 2176d09ba1a9f48f3f37988015f3992234a5e24f

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>