Add 'time_taken' of each check to JSON response

[Samuli Kohomäki]

I like to use the JSON response with load balancer. Less data transferred.

But once health check takes long, there is no information, which check took long.

The HTML response has the durations but if you have to read the actual response in terminal etc. it's quite unreadable

plugin.time_taken could be added to the JSON response as well. The JSON response is much more readable as it is (even without any indent).

[Johannes Maron]

Hi @maszaa,

If you built it, I will review it 👍

Best,
Joe

[Jakob Johannes Bauer]

This is now implemented in v2 of the API in PR #295