The "/chat-send" page:

This page receives (via XHR) a new chat-message and/or a new file to be entered into the chat history.

On success it responds with an empty response: the new message should be fetched via /chat-poll. On error, e.g. login expiry, it emits a JSON response in the same form as described for /chat-poll errors, but as a standalone object instead of a list of objects.