Tell user about bonus amount when doing credit card top up

Merge branch 'credit-card-bonus'

* credit-card-bonus:
  Insert bonus when paying by credit card

Insert bonus when paying by credit card

Refactor BuyAccountCreditForm

add_to_form no longer needs a promise or a network call, instead we use
a factory to get that data up front and inject the dependency.

New BuyAccountCreditForm#parse to get the relevant data back out of an
XMPP form.

Some changes to Transaction and sgx_jmp.rb to use the new method
semantics.

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

* new-signup-credit-card-decline:
  Block repeated declines for 24 hours
  Handle credit card decline

Block repeated declines for 24 hours

Split logic out into testable objects

Rubocop clean. Good test coverage of helper objects.