Browser page view (BPV) are tracked currently via specific HTTP request headers which we attach on AJAX/MessageBus polling requests and refer to as the "piggyback" method or via the new dedicated `/srv/pv` endpoint when the `use_beacon_for_browser_page_views` site setting is enabled. For the "piggyback" method, details about the BPV request headers are never logged while the `/srv/pv` endpoint is handled by the `Middleware::RequestTracker` and never hits the Rails controllers. As a result, any attempt to debug errors with regards to BPV is hard because we have no visibility into how the actual params of these BPV related requests arrived at the server.
This commit updates `Middleware::RequestTracker` to fire `process_action.action_controller` notification whenever a request results in BPV counters being incremented so that a log line lands in the configured Rails log file where the request's params field contains the attributes that was sent from the client.
"piggyback" BPV requests are logged using a fake controller#action reference of "PageviewController#piggyback" while the beacon BPV requests are logged using a fake controller#action reference of "PageviewController#beacon".