Add async iterator for query results

[NSeydoux]

This adds a helper function to make it easier to go through all of the paginated results. It allows syntax like the following:

  const pages = paginateQuery({ type: "SolidAccessGrant", status: "Active" },
    {
      fetch: session.fetch,
      queryEndpoint: new URL("https://vc.inrupt.com/query"),
    });
  let i = 0;
  for await (const page of pages) {
    console.log(`Page ${i} has ${page.items.length} items.`)
    i += 1;
  }

Unit tests aren't completely thorough, because technically they should check for all the error conditions, which are already checked in the underlying query function. I don't think it's worth the overhead.

[edwardsph]

Really nice approach. Ideally we'd have tests that covered 0, 1, and 2 pages to account for different conditions in the generator

[NSeydoux]

Yes, I'll add more unit tests for sure. And I'm not 100% sure the name of the function is descriptive of what it does, paginating results is what the server does technically, this goes through the pages, but I haven't found a more suitable name yet.

[edwardsph]

You previously had return here and I looked up why. It not only yields the last page but marks the iterator as done so I thought you were right. Why do you think it should be yield?

[NSeydoux]

That's what I initially expected too, and that's why I had a return, but in tests that didn't work as I expected. If I understood correctly, the iterator has a return function to mark it done, but here the function is a generator, which returns said iterator, hence the difference. None of the generator examples in the MDN docs use return, and here is an example in the Node CLI:

> function* test() {
... yield 1;
... yield 2;
... yield 3;
... return 4;
... }
undefined
> const i = test()
undefined
> Array.from(i)
[ 1, 2, 3 ]