Basic batch mode to copy attestations from a cache
Implements #31
Untested, since #89 is close and it probably makes sense to test them together
No retries or parallelism, that doesn't seem necessary at this point.
Only problem from my test: crashes when it doesn't find one path.
Ah, the intent was for those to get added to the failed list but it's very possible I messed up the error handling somewhere. A backtrace would've been good but I suspect it'll be easy to reproduce.
(rebased to fix conflicts but haven't looked into the error handling yet, somewhere in the next few days, I'll self-assign when I start work on it)
Easy reproducer: evaluation #12