date32 fields (days since 1970-01-01) are converted into timestamp fields

[tom-webber]

The current handling of date type columns by metadata schema means that fields specified as date32 (days since 1970-01-01) are converted into timestamp fields, when they should be date fields. No extra precision is gained by adding the timestamp, and may cause mismatch if the desired output is truncation of the timestamp to date.

A proposed solution would be to create a table_schema_2.json or equivalent with the addition of a date type_category for date32 fields. This should then become the default for tables going forward.