Track a batch of product events

For an app that ingests asynchronously the valid events are durably queued and applied shortly after, in accept order; accepted counts them and rejected counts the events validation dropped. Events the database later refuses (a derived event code, a contact-rule violation) are dead-lettered one by one rather than counted. Events from known crawlers and bots (every event when the request's User-Agent is one, otherwise each event whose context.user_agent is one) are dropped without being stored but counted under accepted, so SDKs do not retry them.