Fix aio with Anys

[slessans]

This attempts to fix some of the asyncio issues by converting metadata to Anys. Not particularly proud of the solution, but may be an OK band-aid in the meantime if it can get things unblocked. All the rest of the code is the original code from #15

[shabbyrobe]

Thanks again for picking this up. I'm definitely keen to see this sorted out too, great to see some progress!

In my response to issue #20, I hoped you might be able to provide some representative usage snippets:

[...] Would you mind sharing a couple of representative, anonymised, ideally self-contained snippets with me here? That will make it much easier for me to get up and running and also give me some ready-made use cases to try to target with some tests.

Having already had to revert this particular feature once before due to quality issues, I'm reluctant to merge anything without quite a few of these snippets turned into test cases. Even if it's just snippets in comments here, then I can add tests myself, I don't mind. But I do want to be much more careful to minimise potential disruption this time, as this is by no means a trivial addition and I'm concerned that I'm not using this feature enough myself at the moment to be able to get the nuance right.

[shabbyrobe]

Closed due to inactivity. Feel free to reopen with MREs any time.