Set Content-Type header in response

[hkjn]

Since we return JSON, we should set Content-Type=application/json.

This messes up some monitoring we have, since it receives the default Content-Type: text/plain; charset=utf-8 currently, and expects only JSON for its health checks.

Tested by building and running sample program before/after change.

Before

curl -v http://localhost:8077/healthcheck
*   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 8077 (#0)
> GET /healthcheck HTTP/1.1
> Host: localhost:8077
> User-Agent: curl/7.52.1
> Accept: */*
>
< HTTP/1.1 200 OK
< Date: Fri, 17 Mar 2017 10:05:54 GMT
< Content-Length: 117
< Content-Type: text/plain; charset=utf-8
<
* Curl_http_done: called premature == 0
* Connection #0 to host localhost left intact
{"healthy":[{"actionable":true,"healthy":true,"name":"Sample Check","type":"SELF","dependent_on":{}}],"unhealthy":[]}

After

curl -v http://localhost:8077/healthcheck
*   Trying ::1...
* TCP_NODELAY set
* Connected to localhost (::1) port 8077 (#0)
> GET /healthcheck HTTP/1.1
> Host: localhost:8077
> User-Agent: curl/7.52.1
> Accept: */*
>
< HTTP/1.1 200 OK
< Content-Type: application/json
< Date: Fri, 17 Mar 2017 10:13:58 GMT
< Content-Length: 117
<
* Curl_http_done: called premature == 0
* Connection #0 to host localhost left intact
{"healthy":[{"actionable":true,"healthy":true,"name":"Sample Check","type":"SELF","dependent_on":{}}],"unhealthy":[]}

[alde]

Good catch :-)

👍