http active health check

[smaznet]

add a way to check upstreams via http request

defined a endpoint on my host /healthy which returns ok on success currently i used haproxy but i want switch to caddy

example config in http health check:

"active": {
			"port": 0,
			"interval": 0,
			"timeout": 0,
			
			// new fields
			"type": "http",
			"host": "my-host.com",
                        "path": "/health",
                        "expect_status": 200,
			
		},

[mholt]

This is open if anyone would like to work on this (I don't have the time currently)