pin to riverpgxv5@v0.0.1

[bgentry]

To make this work, also set up a replace directive to use the local riverpgxv5 from within the river package's go.mod.

I tested this locally from our riverdemo test app and confirmed that I was able to import riverpgxv5@v0.0.1, and then even tested with a locally tagged river@v0.0.2 and was able to use that at the same time.

The gomoddirectives linter does not allow any replace directives by default, but we can customize that to allow this one replace if you think this seems sane.

[bgentry]

You would think I would be able to use the replace-allow-list option, but no, that still fails due to the local replace path. So I just have to allow all local replaces afaict.

[brandur]

Think it looks sane?

I was trying to read what the effect of a replace was on other projects that might be importing River. The Go Modules reference says this:

replace directives only apply in the main module’s go.mod file and are ignored in other modules. See Minimal version selection for details.

I think that means it won't affect anything else? But as usual with Go documentation, the wording is too vague/ambiguous to say anything for sure.