+ # Report and error to the user
+ # (If anyone ever fixes Rails so it can set a http status "reason phrase",
+ # rather than only a status code and having the web engine make up a
+ # phrase from that, we can also put the error message into the status
+ # message. For now, rails won't let us)
+ def report_error(message)
+ render :nothing => true, :status => :bad_request
+ # Todo: some sort of escaping of problem characters in the message
+ response.headers['Error'] = message
+ end
+
+private
+
+ # extract authorisation credentials from headers, returns user = nil if none