MySQL 0000-00-00 to null, but field was not null

[FreCap]

MySQL currently allows 0000-00-00 as a valid value, Postgres doesn't and converts it to a null value.

However in case it is converted to null value, and the column in the original MySQL was not null (hence also in postgres is not null), it breaks.

A hack in pg_lib.py can be:

table_ddl = {}
for column in table_metadata:
    # [patch]
    if column["data_type"] in ["timestamp", "date", "datetime"]:
        column["is_nullable"] = "YES"
    # [end patch]

however it would be nice to put it behind a flag and not make it as a default behavior.

Could you please advise how to easily create a new flag for it and use it in that function?