Reloading the schema cache might reload external config files

[wolfgangwalther]

While hacking on PostgREST/postgrest#2112 I noticed the following:

Our IO tests expect SIGUSR1 to reload the schema, but not the config files - and therefore not reload the @/external_file for jwt-secret either.

https://github.com/PostgREST/postgrest/blob/6b5370f145ad2f346ec803c0ddaa3f47ab86ed76/test/io/test_io.py#L554-L562

However, that's not entirely true: Once we have db-config=true, the config is indeed reloaded and those external files as well.

I didn't test, but I assume in this case the full config file is reloaded when the schema cache is reloaded.

I don't see us changing any of that at the moment, so maybe we should just add a hint in the docs at the "schema reloading" section mentioning, that reloading the schema with db-config=true will reload the config (db + file), too?