support function timezone(zone, timestamp)

[lmatz]

Is your feature request related to a problem? Please describe.

The function timezone(zone, timestamp) is equivalent to the SQL-conforming construct timestamp AT TIME ZONE zone.
https://www.postgresql.org/docs/current/functions-datetime.html#FUNCTIONS-DATETIME-ZONECONVERT
We have the latter

Describe the solution you'd like

No response

Describe alternatives you've considered

No response

Additional context

No response

[dttung2905]

Hi @lmatz, im new to this but interested in the issue. Do you have any pointers where to start?

[lmatz]

Hi @dttung2905

Appreciate your interest in contributing to RW!
https://github.com/risingwavelabs/risingwave/blob/main/src/expr/impl/src/scalar/extract.rs is a time-related function, you can mimic the way how it is integrated into the codebase.

Feel free to assign the issue to yourself! Thanks

[dttung2905]

@lmatz thank you for the pointer. I will take a look at it today. You can assign it to me 🙏