@UnstableApi
    static HealthCheckUpdateHandler of() {
        return DefaultHealthCheckUpdateHandler.INSTANCE;
    }
Returns the default {@link HealthCheckUpdateHandler} that accepts a JSON object which has a boolean
property named {@code "healthy"} for a {@code PUT} or {@code POST} request. A JSON patch in a
{@code PATCH} request is also accepted.

<p>For example:
<pre>{@code
// Update healthiness of the server to unhealthy
POST /internal/health HTTP/2.0

{ "healthy": false }

// Patch healthiness of the server to unhealthy
PATCH /internal/health HTTP/2.0

[ { "op": "replace", "path": "/healthy", "value": false } ]
}</pre>
core/src/main/java/com/linecorp/armeria/server/healthcheck/HealthCheckUpdateHandler.java