Also a little more frontend to handle possible failure modes

Still not testing the web code path but ... types and stuff!@

Connections could probably be in a per-thread cache or something but
redemption costs are going to dwarf database opening costs.

Also, filesystem caches and no benchmarks and all that.

A separate connection per concurrent transaction is required.

transaction rollback logic relied on exceptions, stripe charge function
signaled failure with Either, thus stripe failues had no effect on transaction
rollback

`catch` is not a good way to assert something is thrown

This does a better job covering good and bad cases in the implementation,
though currently none of the values resulting are used so they're still not actually covered.

not sure if it is a good idea to combine them though

It's sort of a meaningless change.  Blech.

on advice of #haskell, going to try hedgehog instead