FC-0001: ecommerce Basket Page -> micro-frontend (make the column nullable)

[UvgenGen]

Description

This is a first part of removing ecommerce's older implementation of the Django-server-side rendering of the Basket Page. Second part: https://github.com/openedx/ecommerce/pull/3718

Updated the model and generate a migration making the column nullable (null=True)

Supporting information

https://github.com/openedx/public-engineering/issues/68 Original Jira Issue: https://openedx.atlassian.net/browse/DEPR-42 PR to edx-platform: https://github.com/openedx/edx-platform/pull/30377 Second part: https://github.com/openedx/ecommerce/pull/3718

[openedx-webhooks]

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