[TOP-2] Add endpoint for health checking

[tuxpiper]

For load balancers to properly operate with the API, it's necessary to have a designated health check endpoint. In its most basic form, this can be a simple route that simply returns "OK" (or { "health": "OK" } if we are so inclined to have JSON everywhere). What matters to the load balancer is the HTTP response status (usually 200 is expected)

The trick in our case is this: the load balancer will not provide any hostname in the HTTP request (remember HTTP version 1.0?). This means that the request will be handled by the default virtual host in nginx , and that the PHP code will not receive any hostname header. This is relevant for our platform cloud hosting, where we always expect to know if the request is coming for deployment1.ushahidi.io or deployment2.ushahidi.io .

The health check route can't depend on any of that.

_USH-642

[tuxpiper]

@rowasc this is the health check endpoint issue that I mentioned yesterday.

[rowasc]

was this done? 🤔

[tuxpiper]

@rowasc nope, not that I know of