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

Helper to get a promise that resolves after N seconds

Helper to allow using sync-style code in a Promise context

This helper spins up a fiber and returns an unresolved EMPromise, then runs the
passed-in block inside the fiber and fulfills the promise with the result of the
block. Because nothing is looking for the Fiber to return it is free to act as a
trampoline for EMPromise#sync and other fiber-sync-style code that does not
block the EM reactor.

Split logic out into testable objects

Rubocop clean. Good test coverage of helper objects.