window.postmessage for Interactive Auth fallback
window.postmessage for Interactive Auth fallback

If you're a webapp running the fallback in an iframe, you can't set set a
window.onAuthDone function. Let's post a message back to window.opener instead.

matrix-org/synapse,matrix-org/synapse,TribeMedia/synapse,matrix-org/synapse,matrix-org/synapse,matrix-org/synapse,matrix-org/synapse,TribeMedia/synapse,TribeMedia/synapse,TribeMedia/synapse,TribeMedia/synapse