Add weekday, unix_date Spark function

[acvictor]

Description

weekday
Returns the day of the week for date as 0 = Monday, 1 = Tuesday, …, 6 = Sunday.

Differs from dayofweek which returns the day of the week for date as 1 = Sunday, 2 = Monday, ..., 7 = Saturday.

Spark function docs - https://spark.apache.org/docs/latest/api/python/reference/pyspark.sql/api/pyspark.sql.functions.weekday.html

unix_date
Returns the number of days since 1970-01-01.

Spark function docs - https://spark.apache.org/docs/latest/api/python/reference/pyspark.sql/api/pyspark.sql.functions.unix_date.html