Re: Custom oauth validator options

> Might be more reason to look into the GUC system?

I am already thinking about that, I have some ideas for a proof of
concept, but no working prototype yet. But without requiring
shared_preload_libraries, we can't do early error reporting during
postmaster startup about custom parameters. Is that okay? GUCs already
work this way, and this could be a bit safer (reporting unknown
parameters/refusing to proceed during login, when we can completely
parse all parameters), but it would be different compared to how
pg_hba is handled currently.