Add support for WEEK function #291
Description
Goal: add support for a function that takes in a datetime value and returns what week of the year it belongs to as an integer. This should work a lot like Snowflake's WEEK function (bear in mind complexities like its WEEK_OF_YEAR_POLICY and considerations of ISO weeks.
Before starting this issue, the following decisions need to be made:
- What is the behavior of this function as far as how the first/last week are defined?
- Is the first week 0 or 1?
- How are the two behaviors above controlled by PyDough config variables, if at all?
- If there are config variables, what should the defaults be?