NEL reports grouped by one dimension

The reports of POST /analytics/nel grouped by one dimension.

One row per value with its weighted error_count, its affected_visitors, its share of the weighted reports of the whole answer, and first_seen_at and last_seen_at, the browser's time of its first and latest report in the window. order_by puts the most weighted reports first by default, or the newest group first with last_seen_at, a tie by key. The filters, the weighting, meta.sampling and the limits of the visitor count are those of the aggregate route.

Every key but those of phase, method and protocol, which have no filter, is a filter value that selects its row's reports. page_url groups by the page the failed request was sent from, as stored. Reports without one form a row with an empty key, which filters.page_url cannot select, since an empty value is no filter. The same holds for a request URL without a path, the empty path key and a request_url key without a /. A page_url or path key holding * is read by its filter as a wildcard. host, bot_name and error_type keys go back as one-value lists of the filter of the same name. A stitch key goes back as filters.stitch: [key], a status_code_range key as filters.status_code_range: {gte: key, lte: key}. A request_url key is host and path in one, and splits at its first / into filters.host: [host] and filters.path: path. Reports without a stitch or without an HTTP response form the row with the empty key of these dimensions, which no filter selects.

A site_id row's last_seen_at tells whether a site's NEL header reaches browsers.