Using Roundcube+Plugins+DAV files without LDAP

[Ed W]

Hi, I have an existing setup which is based around an internal mysql 
database. We have a bunch of infrastructure built inhouse which 
maintains users in that, etc.  However, what you guys are doing with 
roundcube, the calendar and contacts integration and the new DAV file 
storage is just fantastic and I would like to figure out how I might 
integrate it with my mysql backend

I have poke around the current git source and it seems like there is 
great encapsulation of nearly all the major components, including the 
LDAP auth.  However, I also see reference to IMAP based auth?

Would someone be kind enough to give me a quick overview of what I will 
need to change to fully integrate with a mysql based DB, rather than 
IMAP? As near as I can see, not many changes are needed, but I can't 
tell yet whether I will need to implement my own auth or whether I can 
just use the normal roundcube auth?  Also I don't understand where the 
addressbooks are being stored from eyeballing the code, phrased in a 
bigger picture way, where else do you use LDAP and hence where might I 
need to re-implement an integration to avoid breaking things?

Grateful for a leg up here.  From what I can see, fantastic code 
abstraction which should actually make this quite possible - thanks!

Ed W