small project idea #71503: have ezmlm store subscribe and unsubscribe requests

i have roughly a bazillion little ideas and projects floating around. one is to figure out a good way to have ezmlm store (un)subscribe requests (and confirmations) to make it easy to track down what happened when someone got subscribed mysteriously. (actually, a lot of my little ideas involve logging and otherwise storing more information. figuring out ways to mine the collected data can often come later.)