Reverse pagination: hasPreviousPage and before: and last:

[simonw]

For the non-alpha release I'm going to support forwards pagination only - after: and endCursor and hasNextPage. I can support startCursor too at this point even though it's not useful for anything yet.

I'll split hasPreviousPage and before: into a separate ticket.
Originally posted by @simonw in #2 (comment)

[simonw]

This may be blocked by Datasette core support for reverse pagination: simonw/datasette#916 - but I can go ahead and implement this independently and use that implementation to inform a later change to Datasette.

[simonw]

Worth noting that edge order has some rules in https://relay.dev/graphql/connections.htm#sec-Edge-order

You may order the edges however your business logic dictates, and may determine the ordering based upon additional arguments not covered by this specification. But the ordering must be consistent from page to page, and importantly, The ordering of edges should be the same when using first/after as when using last/before, all other arguments being equal. It should not be reversed when using last/before. More formally:

• When before: cursor is used, the edge closest to cursor must come last in the result edges.
• When after: cursor is used, the edge closest to cursor must come first in the result edges.

[simonw]

This is pretty low priority since sort_desc: can be used with first: and after: at the moment.