This is a follow up of the issue MDL-68645 where we discovered that activity modules do it wrong when they create new calendar events and use their description as the event description. We should not format the description text at this point. The raw text and its format should be somehow passed to the calendar, together with all the information on how to copy the embedded files into the calendar scope.

One idea that came to my mind was to use a "clipboard" like object that would have all the information (text, format, embedded files etc) needed and could be used by the calendar API instead of the string (or array in case it comes from the editor).