Add billing agreement created spec
Make receipt id optional
Add paypal refunds
Paypal refunding service and ipn handling
Limit string db fields
Add validations for paypal refund
Merge pull request #673 from sharetribe/ipn-refund-order

Ipn refund order
WTI pull
Draft of api spec for paypal payments
get payment info by transaction id
Use external merchant id, use symbols
Draft of accounts api spec
response bodies for token validation
Draft of billing agreements API
Billing agreement charge + reformat all
format Money types
Payments api skeleton
Add request payment implementation
Helpers for account and success response handling
Payments service, create and cancel_request