feat(dyn-abi): derive Default for TypedData

[DaniPopes]

cc @prestwich is this right or does this need a custom impl to handle resolver/..?

[DaniPopes]

What's a sensible default for no-op / testing then?

[prestwich]

I think it'd be okay if default is always invalid

I would be very against this

why not just add a cfg_attr(test, derive(Default))

[mattsse]

this only works internally I think

[prestwich]

instead of proposing a feature, can you talk about the need? what are you trying to test?

[DaniPopes]

dummy input to eth_signTypedData, currently I can only instatiate it from json or sol struct

[prestwich]

sure but do you want input that's going to cause an error, GIGO, or something else?

[gakonst]

if useful for testing we have used test-utils features in the past instead of cfg_attr(test), and i'd be ok w it