unable to build with aeson 2.0

[DougBurke]

So, it looks like the main relevant change is that rather than (Text, Aeson.Value) we now have (Aeson.Key, Aeson.Value) for dictionary elements. hvega has a number of types that have (Text, Value) in them and we can

• change the type to now use (Key, Value)
• retain the type and just internally add a bunch of fmap (first Aeson.Key.fromText) using CPP to support old and new aeson.

We could do option 2 (allowing people to use aeson < 2) and then, once aeson 2 support has stabilised in the ecosystem, add option 1 (ie force aeson 2).

It's not clear to me yet whether there's any other change needed, which could complicate things.

[DougBurke]

We are also blocked (for testing only) by

• Doesn't build with aeson >=2 informatikr/aeson-pretty#36

[DougBurke]

Closed by #191 (although may need some cabal updates for when aeson-pretty is fixed).