Re: Improving GUC prefix ownership for extensions

> Do we really want the grief of making it mandatory?

I didn't suggest making it mandatory - the current patch I attached is
completely opt-in (default setting is exactly how it works currently,
DBAs have to opt in by changing it).

What I mentioned is that we could make it opt-out

1. by making the warning the default, which still allows everything
allowed currently, and doesn't change behavior at all, other than
writing a few warnings to the logs
2. and later maybe changing it to a more strict default, but still
keeping the GUC, so users can opt out

But that part is optional, we could simply leave it completely relaxed
by default.

My reasoning for making the warning the default is to encourage
extension developers to properly reserve GUC prefixes, without causing
compatibility problems for users - but I'm not sure about that, that's
why I submitted the patch with "off" default.