[airbyte_destination_snowflake] retention_period_days is not truly optional

[sw-lkinsella]

In the docs for the Snowflake destination provider it says retention_period_days is Optional, however this is only partly true. If we don't supply it you then default to a retention_period_days = 1.

The problem with this is you're enforcing a set value regardless. However in Snowflake it's not unusual to have this controlled from a higher level, for example at the database or account level.

Make this truly optional so if it is omitted you simply do not set it and allow it to be inherited.