Introduce Decimal helper type

[adampetro]

Introduce a helper type for Decimal scalars to handle conversion to/from f64.

Note that in this implementation, it removes the Eq implementation in generate_types! because f64 does not implement Eq. Hopefully this is not an issue as we'll still have PartialEq which goes a long way.

[surma]

Looking good, although I wonder if it might be handy to implement Deref<Target = f64> for this type. We’d get most of the behavior for free.

[adampetro]

Looking good, although I wonder if it might be handy to implement Deref<Target = f64> for this type. We’d get most of the behavior for free.

I had this in a previous iteration but opted to remove it based on this guidance on Deref usage from the docs:

Deref should only be implemented for smart pointers to avoid confusion.

But I don't have a strong opinion on this and I'm happy to add it if you think it would be beneficial.

[andrewhassan]

LGTM!

For release, this is technically a breaking change, right? Partners will have to update their Rust code to use Decimal instead of String, right?

[adampetro]

For release, this is technically a breaking change, right? Partners will have to update their Rust code to use Decimal instead of String, right?

Yes. But since it's pre-1.0 I think it's ok to have breaking changes in a "minor" version bump.