# Try to load the mentity from uri with `/:id`.
	#
	# Send 400 if `:id` is null.
	# Send 404 if no entity is found.
	# Return null in both cases.
	fun mentity_from_uri(req: HttpRequest, res: HttpResponse): nullable MEntity do
		var id = req.param("id")
		if id == null then
			res.api_error(400, "Expected mentity full name")
			return null
		end
		var mentity = find_mentity(id)
		if mentity == null then
			res.api_error(404, "MEntity `{id}` not found")
		end
		return mentity
	end