check_http: Optionally return content

[towolf]

When using check_http on an API with a healthz endpoint, this is basically useless:

I'd like to see the content that the HTTP request response is returning. It's actually stating that an API on the internet that it is using is down. So I can't do anything and can ignore this problem.

[towolf]

I know that I probably don't want to return long HTML page content, but a flag to also include the body text would be sweet and I can't really believe that this is not supported?

[towolf]

Here's another example:

./plugins/check_http -H lobby-api.example.com -u /health -S
HTTP OK: HTTP/1.1 200 OK - 746 bytes in 0,119 second response time |time=0,119410s;;;0,000000;10,000000 size=746B;;;0
{"status":"UP","database":{"status":"UP"},"migration":{"status":"UP"},"rabbitMQ":{"status":"UP"},"redis":{"status":"UP"}}

I will try to make a PR with an optional flag to return the content.

[towolf]

Thanks for merging.

Here's an example where this is useful, Gitlab:

Before

# /usr/lib/nagios/plugins/check_http -I 127.0.0.1 -S -u /-/liveness
HTTP OK: HTTP/1.1 200 OK - 654 bytes in 0,039 second response time |time=0,039068s;;;0,000000 size=654B;;;0

After

# ./check_http -I 127.0.0.1 -S -u /-/liveness -B
HTTP OK: HTTP/1.1 200 OK - 654 bytes in 0,039 second response time |time=0,039184s;;;0,000000;10,000000 size=654B;;;0
{"db_check":{"status":"ok"},"redis_check":{"status":"ok"},"cache_check":{"status":"ok"},"queues_check":{"status":"ok"},"shared_state_check":{"status":"ok"},"gitaly_check":{"status":"ok"}}

[towolf]

Now we just need a release ...