Export data - Add possibility to name multiple extracted files from a column

As of now, blob files can be named after a set of fixed variables, after selecting a bunch of rows from the resultset of a query.
It would be very nice to add the possibility to use the content of a column as filename.

For instance, If I had an Oracle database **Table** and used the folloqung SQL to query it, it would be nice to use the concatenated value of **fn** as filename.

SELECT blob, User || '_' || Timestamp || '.pdf' AS **fn**
FROM **Table**

The issue names no files, tests, or entry points. Start by tracing the result-set blob export flow and how fixed filename variables are handled; done means a selected column expression can provide each extracted file's name while existing naming options continue to work.

Written by the indexing model from the issue text.