[horde] Adding fields to session data

[Kevin Konowalec]

We are currently running several front-ends to horde and I want to be  
able to tell what machine users are on at any given time.  I'm  
thinking the best way to do that is to add a field to the serialized  
session data with the machine name they last connected to (they are  
round-robining between the machines so they can start on one and  
finish on another transparently).  So I'd want to add some code that  
would add or modify that field on every connection - which shouldn't  
be too onerous considering the session data gets updated on every  
connection anyway.  My questions are a) what would be the best place  
to add that code? and b) In general are local modifications and  
tweaks like that a bad idea?  Would they cause any problems when it  
comes to upgrading to the latest versions?