fetchKycInBrowser: postMessage doesn't work if the form is multi-page

[morleyzhi]

Right now, fetchKycInBrowser attaches a postMessage event listener only when the iframe is initialized. But this is a problem if the interactive flow has multiple pages: a second page load will no longer have the onMessage listener.

Some options:

• Set the listener someplace other than the interior window context
• Constantly re-check that the event listener is in place