For controlling a session when the iframe is open, it may be necessary to provide hooks into Manticore's UI that Roundcube can use.

For this, I shall expose an API that uses postMessage for cross-window event handling.

An example use case would be an "Invite" button drawn by Manticore, which works thusly:

1. For standalone Manticore, the Invite button would pop up a dialog listing possible collaborators sourced from Mongo.
2. For the Kolab-Manticore combination, clicking the Invite button would fire an event inviteButtonClicked, that Roundcube can listen to and consequently display an invitation dialog populated with Kolab users.