public HealthCheckServiceBuilder unhealthyResponse(AggregatedHttpResponse unhealthyResponse) {
        requireNonNull(unhealthyResponse, "unhealthyResponse");
        this.unhealthyResponse = copyResponse(unhealthyResponse);
        return this;
    }
Sets the {@link AggregatedHttpResponse} to send when the {@link Service} is unhealthy. The following
response is sent by default:

<pre>{@code
HTTP/1.1 503 Service Unavailable
Content-Type: application/json; charset=utf-8

{ "healthy": false }
}</pre>

@return {@code this}
core/src/main/java/com/linecorp/armeria/server/healthcheck/HealthCheckServiceBuilder.java