- remove warnings that are occuring during compilation
- TO_BS_DATE(string, format): Converts a string with a specified format into a BS date value.
- explicit type cast from bs_date to date and vice versa such that we are able to select a date columm from a table and cast it with bs_date and vice versa
 (also check if implicit type cast would be better for this. But I think that would be pretty messy since casts may happen in unintended places/queries)
- pgxn deployment
- test compatibility on earlier PostgreSQL versions (look for approaches to achieve this, maybe making use of containers)
- ci pipeline

[DONE]
- error handling, currently we are outputing to stderr (need to raise error on PostgreSQL instead)

[DONE]
- CURRENT_BS_DATE

[DONE]
(Instead of having all of these, make the ad_to_bs function return a bs_date object that can be passed to a TO_CHAR like function)
- ad_to_bs_en
- ad_to_bs_np
- bs_to_ad_en
- bs_to_ad_np

[DONE]
(We overloaded the to_char function for the same purpose instead)
- BS_DATE_TO_CHAR(bs_date_value, format): Formats a BS date into a custom string representation (e.g., converting YYYY-MM-DD to DD/MM/YYYY).

[DONE]
- Add devanagari support on the TO_CHAR like function or if not possible, create a separate function for that.

[DONE]
- remove warning generated by bs_date in/out functions ("should not be volatile")