[tor-relays] Reimbursement of Exit Operators

[Damian Johnson]

> Unless maybe stem already does exactly this for us?

Yup, stem parses the extrainfo descriptors...

https://stem.torproject.org/api/descriptor/extrainfo_descriptor.html#stem.descriptor.extrainfo_descriptor.ExtraInfoDescriptor

The only pesky bit is that you'll need to download a lot of
descriptors from metrics (I assume you need the entries published over
a long period of time?).