How are you typically dealing with rolling upgrades of event sourced
apps? Specifically, if you have 3 servers, upgrade the first from v1
to v2, which now starts creating v2 events, and then the other servers
with v1 receives these events, what do you do? Close the subscription
and wait to be upgraded? Maintain two stream positions (one which you
will reread upon restart, and one with where you have successfully
read AND understood)? Any other tricks?