have a story for pagination

[ethanpailes]

At the least, there should be an example showing how to do it. It is not clear to me if we would want to make any changes to the core pggen library though.

[ethanpailes]

Since writing this, I've implemented pagination using pggen, and it is a bit of a pain to do full bidirectional pagination with a static SQL query. Dynamic sql metaprogramming really is the most natural way to do this. We could provide some custom functionality in the same way that we handle updates and upserts, but I'm a bit concerned with that approach since there are so many different ways to do pagination.