Add logging

[bruth]

Use Onelog with JSON output.

[gracebrownecodes]

Why onelog instead of zerolog?

[bruth]

Mainly to try it out, but either is fine. This is a small isolated project, so it is a good candidate to try it out (in the end I don't really care especially if someone else implements it). The functional approach to adding fields is interesting. Likewise the output are the same (both JSON) so changing between them would be transparent from the consumer standpoint if need be.