Distributor Price Import: Option to update existing products only (skip product creation)

Description:

When importing distributor prices, we currently have no way to limit the import to only update pricing on products that already exist in our catalog. The import will create new products if they don't exist yet, which is not always the desired behavior.

We would like an additional toggle in the "Import Distributor Prices" dialog that allows us to choose whether new products should be created during the import, or whether the import should only update pricing on already-existing products — skipping any items that don't have a match in our catalog.

Use case:

When we want to refresh pricing on our existing catalog without expanding it, we need this control. Currently there is no way to prevent new products from being created during a price import, which requires manual cleanup or cross-referencing before uploading.

Proposed behavior:

A toggle such as "Only update existing products" that, when enabled, causes the importer to silently skip any distributor line items that do not match an existing product in the catalog — no new products are created.

Current workaround:

Manually cross-referencing the distributor file against the existing product catalog before uploading to remove non-matching items.