Create/Update Product is Missing external_id Property

[AlexAntonides]

Bug report

Describe the bug

I'd like to be able to add an external_id to my product, however, both the CreateProductDTO and the UpdateProductDTO don't contain options to add an external_id to any of my products.

I've found two other relating issues from a year ago (#4388, #2497), both are closed, which indicates me it might've been an option in v1, but in v2 this option has disappeared.

System information

Medusa version (including plugins): rc / v2.0.10
Node.js version: 20
Database: Postgres v10.4
Operating system: macOs 15.0

Steps to reproduce the behavior

1. Create a product through the API with an external_id.
   or
2. Update a product through the API with an 'external_id'.

Expected behavior

You should be able to assign an external_id to a product.