[Backport] #22869 - defaulting customer storeId fix

[Wirson]

Description (*)

Backport pull request
Fix prevent saving default customer storeId if one was not passed in rest request. StoreId is taken from previously loaded customer data if none is provided.

Fixed Issues (if relevant)

1. REST: Updating a customer without store_id sets the store_id to default  #22869: REST: Updating a customer without store_id sets the store_id to default

Manual testing scenarios (*)

1. use steps provided in issue description

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds are green)

Backport for: #22893

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[dmytro-ch]

Hi @Wirson, could you please merge the latest changes from 2.2-develop into your working branch, and update it according to original PR.
Please, also fix the integration test if necessary.

Thank you!

[Wirson]

Hi @Wirson, could you please merge the latest changes from 2.2-develop into your working branch, and update it according to original PR.
Please, also fix the integration test if necessary.

Thank you!

Code updated. I did not remove lines removed in original PR due to failing tests. Just a code style refactor.
Failing integration tests are only skipped, right now no tests really fail.

[magento-engcom-team]

Hi @dmytro-ch, thank you for the review.
ENGCOM-5188 has been created to process this Pull Request

[m2-assistant]

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