Method to bill the plan of a Customer

Bills their balance for the cost of one month of plan.
Activates the plan by insert into plan_log, unless already active in which case
extends current plan by one month.

Merge branch 'register-command-first-pass'

* register-command-first-pass:
  Add sourcehut CI
  Add Rakefile to run all tests
  Initial registration flow for Bitcoin
  Registrations that start on the web will have a tel selected already
  Helpers for doing Electrum RPC
  Add helper to fetch current BTC sell prices
  Allow skipping tests without being caught in pry

Initial registration flow for Bitcoin

This is the Bitcoin "happy path" where there is already a tel and a customer_id.
Gets all the way to generating a BTC address for payment and quoting an amount.
Stubs out flows for credit card and activation code as well, but does not
implement those flows.

TBD: after bitcoin payment comes in and jmp-pay activates the account, we should
come back here to actually buy the number, select a new one if no longer
available, etc.

Split logic out into testable objects

Rubocop clean. Good test coverage of helper objects.