class Protocol::HTTP::Header::Priority

@returns [Integer | Nil] the urgency level if specified, or `nil` if not present.

Note that when duplicate Dictionary keys are encountered, all but the last instance are ignored.

The urgency level, if specified using `u=`. 0 is the highest priority, and 7 is the lowest.

def urgency(default = DEFAULT_URGENCY)
	if value = self.reverse_find{|value| value.start_with?("u=")}
		_, level = value.split("=", 2)
		return Integer(level)
	end
	
	return default
end