HealthCheck endpoint does not support HTTP Method HEAD

[kris-evans]

I was attempting to curl a healthcheck endpoint as part of a wait-for-it script in Docker and noticed an issue with the HealthCheck server. The server, by default, doesn't respond to the HTTP Method HEAD which is often used with curl to limit the response.

Example with --head

# curl -v --head http://api:8071/_ready
*   Trying 172.22.0.8...
* TCP_NODELAY set
* Connected to api (172.22.0.8) port 8071 (#0)
> HEAD /_ready HTTP/1.1
> Host: api:8071
> User-Agent: curl/7.52.1
> Accept: */*
> 
< HTTP/1.1 405 Method Not Allowed
HTTP/1.1 405 Method Not Allowed
< Content-Type: text/plain; charset=utf-8
Content-Type: text/plain; charset=utf-8
< X-Content-Type-Options: nosniff
X-Content-Type-Options: nosniff
< Date: Fri, 17 Jan 2020 19:55:24 GMT
Date: Fri, 17 Jan 2020 19:55:24 GMT
< Content-Length: 19
Content-Length: 19

< 
* Curl_http_done: called premature == 0
* Connection #0 to host api left intact

Example without --head

# curl -v http://api:8071/_ready
*   Trying 172.22.0.8...
* TCP_NODELAY set
* Connected to api (172.22.0.8) port 8071 (#0)
> GET /_ready HTTP/1.1
> Host: api:8071
> User-Agent: curl/7.52.1
> Accept: */*
> 
< HTTP/1.1 200 OK
< Content-Type: application/json; charset=utf-8
< Date: Fri, 17 Jan 2020 19:55:32 GMT
< Content-Length: 3
< 
{}
* Curl_http_done: called premature == 0
* Connection #0 to host api left intact

When calling the GET endpoint with the HEAD method should just return the HTTP header and a 200.