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...

Ask electrum to notify on new BTC addresses

Otherwise we won't know when someone has paid...

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

Work in the presence of em-synchrony

em-synchrony monkeypatches em-http when loaded. The old functionality is still
present, but under different method names.

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

Helpers for doing Electrum RPC