Create a temporary CSV staging table for a CharlieCard import with a card code, station name, fare and tap time. Give fare a numeric type with a nonnegative check and make the other required fields non-null. Then add a source column with a default of csv and load two rows directly in the statement.
Keep the staging table temporary. Return the two loaded rows with the new source value.
Expected: 2 rows, both with source = 'csv'; the fare values are numeric and the tap times are timestamptz values. The table disappears when the connection ends.