bugfix for available dateparts for redshift/snowflake

[kzzzr]

A minor fix for iso_* dates.

You see Redshift doesn't support isoweek datepart:
https://docs.aws.amazon.com/redshift/latest/dg/r_Dateparts_for_datetime_functions.html

Neither does Snowflake except for DATE_PART function:
https://docs.snowflake.com/en/sql-reference/functions-date-time.html

Database Error in model dim_calendar (models/marts/dim/dim_calendar.sql)
Invalid datetime part for DATE_TRUNC().
DETAIL:
-----------------------------------------------
error: Invalid datetime part for DATE_TRUNC().
code: 8001
context:
query: 760488
location: datetime_ops.cpp:40
process: padbmaster [pid=6610]
-----------------------------------------------

[clausherther]

Hi @kzzzr, thanks for this PR!
I'm going to have to noodle on this for a bit. The implementation of iso_week_end isn't great, you're right isoweek doesn't work there, but you can see here that the "private" _iso_week_end macro ends not actually using the passed in week_type parameter so I should just remove it.

iso_week_of_year is using date_part so should work on Snowflake as you point out, so I'm ok changing the defaults for Redshift, although then we should really just remove the Redshift version and fail if someone wants to use this on Redshift?

[kzzzr]

Greeting Claus @clausherther,
Sure, the solution is totally up to you. I've seen you used "private" macro deliberately.
This is just a quick fix for my deployment and at the same time opportunity to point to this issue.
Great package, by the way. Thank you, enjoy using it.