Summary:
Ref T2787. When Paypal comes back to us with funds on hold, dead-end the transaction but handle it properly.
Generally, smooth out the user interaction on weird states.
Implement refudnds/cancels for Paypal.
Test Plan: {F215230}
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T2787
Differential Revision: https://secure.phabricator.com/D10667
