Outbound call logic for overages

If cannot find an acceptable rate for the number, cannot call.
If balance is too low, cannot call.
If too close to limit, warn.
Else, call.

Represent plan limit details as a useful object

Remove BigDecimal.new

It turns out in newer versions of Ruby this isn't cool anymore.
The new way is BigDecimal(value), which is dumb, but whatever...

monthly_price is in 10000ths of a dollar, not 1000ths

Merge branch 'new-signup-add-credit-card'

* new-signup-add-credit-card:
  Happy path for credit card signup
  Panic should work on any value for error
  Allow getting default payment method, not just index
  Object representing the backend SGX to use
  Stop polluting Object namespace with Blather DSL
  Work in the presence of em-synchrony
  Helper to allow ordering phone number from Bandwidth v2
  Helper to get a promise that resolves after N seconds
  Every payment kind will need the plan, so put it at the top
  Use registration pattern for Payment kinds
  Method to bill the plan of a Customer
  Use Forwardable for simple delegations
  Helper to allow using sync-style code in a Promise context
  New signup: go to web to choose credit card
  OOB helper
  Reject promise on stanza error
  Fix typo

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.