Full review (do not merge)

I used `created_at` in some places because it is guaranteed to be correct, as opposed to `reported_at` which is set by the proxy and can be wrong if the proxy clock is wrong. But then again, the proxy is not guaranteed to send the report within (the default) 30 minutes of reporting it either. So it's probably best to keep it simple - trust the proxy, use `reported_at`, and drop the other timestamps.