Also:
 * post are now HTML and not plain text
 * all event types are returned by
SupportRequest_getCommentPostListAsJson (so that the app can also
display support request used in "traditional" erp5 interface)
 * instead of immediate reindex, we store the "just posted" data in
portal_session.
 * events are created using resource defined as a web site "layout"
property (that's not yet editable)
 * posts do not receive a message-id yet (because ui part is not yet
updated for that), so generate a message-id server side (by just using
id)