Is max-pool-size option global or per cluster worker?
### Summary

I'm trying to track down a "too many clients" error from postgres. While periodically calling `select * from pg_stat_activity`, I notice that an unexpected number of them look to be from postgraphile (among other clients) because they issue queries such as `select json_agg(__local_2__) ...`.

Given that I set `--max-pool-size 8`, I was surprised to see more than 8 connections from postgraphile. But I am also use the `--cluster-workers` option. I noticed that `ps` is showing multiple postgraphile processes and a quick peek at `cli.ts` implies that the workers are forked processes.

That suggests to me that the connection pool size limit is on a per worker basis and is not "globally" enforced by postgraphile. Can someone confirm?

If so, I will need to play with these 2 options to pick a value that is reasonable. If not, does anyone have any idea why the max-pool-size option is not limiting the connections from postgraphile?

### Additional context

I am running postgraphile inside a node docker container.
