Expose arrow-schema serde crate feature flag

[lewiszlw]

Which issue does this PR close?

Expose serde feature

Rationale for this change

What changes are included in this PR?

Are these changes tested?

Are there any user-facing changes?

[tustvold]

Given this doesn't gate functionality in DataFusion, what is the motivation for plumbing it through, as opposed to down streams just declaring this?

[lewiszlw]

Datafusion reexports arrow crate but not reexports all arrow features, users need to add additionalarrow-schema = { version = "46.0.0", features = ["serde"] } to enable serde feature. See https://github.com/roapi/roapi/blob/ea01ffe0d3978af0bb24065e711431bc52e6c96d/columnq/Cargo.toml#L16

[tustvold]

I'm not sure I would expect DataFusion to re-export the feature flags of arrow, but I'll defer to other maintainers

[alamb]

Thank you for the contribution @lewiszlw

The existing feature flags are documented here: https://github.com/apache/arrow-datafusion#crate-features

We currently do have a "simd" flag to enable an arrow feature flag. I think it would be ok to add a serde feature as well

@lewiszlw could you please update the documentation with this new feature flag as well?

[lewiszlw]

Sure, updated.

[alamb]

Thank you @lewiszlw