It would be very useful to be able to configure http-check options for backend like
backend webservers option httpchk http-check send meth GET uri /health server server1 192.168.50.2:80 check server server2 192.168.50.3:80 check server server3 192.168.50.4:80 check
(see https://www.haproxy.com/blog/how-to-enable-health-checks-in-haproxy)