First step of creating an error reporting endpoint that can scale up to WMF traffic:
- set up a second instance of varnishkafka on the bits.wikimedia.org varnish (the first is used by EventLogging)
- configure it with a VSL option to filter on the requests made by the error logger JS module
- create a Kafka topic for JS error reports, and have varnishkafka push the request data there