Create a ThreadFactory that maintains a counter for naming Threads.
name-format specifies thread names - use %d to include counter
daemon is a flag for whether threads are daemons or not

DEPRECATED. Given a `context`, clean up the event stream it represents.

See start-event-stream. This function is for backward compatibility.

Returns an interceptor which will start a Server Sent Event stream
with the requesting client, and set the ServletResponse to go
async. After the request handling context has been paused in the
Servlet thread, `stream-ready-fn` will be called in a future, with
the resulting context from setting up the SSE event stream.

opts is a map with optional keys:

:on-client-disconnect - A function of one argument which will be
  called when the client permanently disconnects.

Starts an SSE event stream and initiates a heartbeat to keep the
connection alive. `stream-ready-fn` will be called with a core.async
channel. The application can then put maps with keys :name and :data
on that channel to cause SSE events to be sent to the client. Either
the client or the application may close the channel to terminate and
clean up the event stream; the client closes it by closing the
connection.

The SSE's core.async buffer can either be a fixed buffer (n) or a 0-arity
function that returns a buffer.