File upload for postgres databases does not let user specify duplicate key behavior

MySQL file upload uses a [`LOAD DATA`](https://dev.mysql.com/doc/refman/8.0/en/load-data.html) statement to import file data into a table. It lets you specify whether you'd like to `ignore` or `replace` on duplicate key.

Postgres file upload uses a [`COPY FROM`](https://www.postgresql.org/docs/current/sql-copy.html) statement. It does not let you specify duplicate key behavior. There are workarounds like [this](https://stackoverflow.com/a/13949654/10555434), where we can import to a temporary table, and then specify on conflict behavior on upsert