Enable import/export of Sales Price for product variants

[Jackob-K]

Module
product_variant_sale_price

Is your feature request related to a problem?
Yes.
While managing products with multiple variants, it is currently not possible to import or export the “Sales Price” field for individual product variants.
Although variant prices can be edited manually in the interface, managing larger sets of variants becomes extremely slow and error-prone without import/export support.
This request is related to—but separate from—issue #431, which concerns a pricing overwrite bug. Even once that bug is resolved, the ability to mass-update variant prices remains an essential missing feature.

Describe the solution you'd like
I would like the module product_variant_sale_price to support the standard Odoo import/export mechanism for variant “Sales Price”.
Specifically:
Export should include each variant and its individual Sales Price.
Import should allow updating variant prices based on variant ID, combination of attributes, internal reference, or barcode.
The system should update only the matching variant price, without touching other variants or the parent template.
This would make bulk updates manageable and prevent hundreds of manual edits.

Describe alternatives you've considered

• Updating variant sale prices manually—too slow and error-prone.
• Manipulating prices via API or SQL—unsafe and not intended for typical business users.
• Using pricelists—does not solve the issue when variant-specific fixed prices are required.

Additional context
Many industries (HVAC, electronics, apparel, etc.) work with products that have dozens of variants where each variant has its own independent selling price.
Import/export support would greatly streamline operations and is expected by most Odoo users managing variant-heavy catalogs.