Server sent events endpoint
Configurable SSE host:port
"client" -> "broker"
Unregistered closed connections

* Also allow CORS
Authenticate SSE endpoint with access token

* Accepts bearer token, Basic Auth or access_token query param
Custom type for a channel of []byte
Don't need that comment
Optional ?raw=1 option streams JSON lines, SSE incompatible.
Go fmt
Encode event only once.
Document the Firehose server
Merge branch 'server_sent_events'