Support more aggregations

[KodrAus]

Looks like there's a new typed_keys parameter we could utilise to parse aggregations exactly.

Since it depends on the parameter being present in the request we would probably have to have an alternative Aggregations parser that expects it to be present.

API Gist

See here

[mwilliammyers]

I think we should add this to #319 (v0.21.0). I am running into the issue of not being able to easily access anonymous aggregations in a project.

I am happy to open a PR to replace the current implementation with your gist.