Support to_json function on struct type

[dharanad]

Is your feature request related to a problem or challenge?

This request is to support to_json in comet apache/datafusion-comet#631. Rather implementing this in comet, i think we should have this function over here and let comet rely on datafusion. Since we also support struct now, this would be a good to have feature.

to_json function Converts a column containing a structs to JSON string. We can incrementally support this functions for other types.

Describe the solution you'd like

TBD

Describe alternatives you've considered

No response

Additional context

No response

[wjones127]

I wonder if this would belong in this repo instead: https://github.com/datafusion-contrib/datafusion-functions-json

[dharanad]

I wonder if this would belong in this repo instead: https://github.com/datafusion-contrib/datafusion-functions-json

I agree datafusion-functions-json is the place for this function. Will re open this issue over there.