#26800 Fixed Undefined variable in ProductLink/Management

[srsathish92]

Description (*)

This PR fixed the issue #26800.
Set product links through API with with empty array of items its throws 'undefined variable' if the product has existing links, So I added the additional condition to check array is empty If yes throws the InputException.
Covered the unit test case with that scenario.
Updated doc blocks in ProductLinkManagementInterface.php with exception class.

Fixed Issues (if relevant)

#26800

Manual testing scenarios (*)

Unit Test: vendor/bin/phpunit -c dev/tests/unit/phpunit.xml.dist app/code/Magento/Catalog/Test/Unit/Model/ProductLink/ManagementTest.php

From API:
URL: /rest/V1/products/1234/links
Method: POST
Data:
{ "items": [] }

(eariler its throws undefined variable if the product has atleast one product link & now its should show valid error message from InputException)

Questions or comments

If any please let me know the feedback's

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)

[m2-assistant]

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[magento-engcom-team]

Hi @aleron75, thank you for the review.
ENGCOM-6983 has been created to process this Pull Request

[engcom-Alfa]

✔️ QA Passed

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