fix: interface conflicts with WooGraphQL v0.21.1+

[justlevine]

What

This PR fixes issues caused by WooGraphQL v0.21.1.

Based on #115 by @robbiebel but with CI that hasn't been autodisabled by github.

Why

• The bug is a side effect of the tech debt mentioned in Interface Error in WPGraphQL IDE #99 (comment)
• fix: "Product" interfaces shared fields fix wp-graphql/wp-graphql-woocommerce#901 decided to make ProductVariation a child of Product (by way of ProductUnion ). I'm not sure if this is a bug or not, but I'll be following up with @kidunot89
• bug in WooGraphQL or no, DX: Can't narrow down interface subtypes on an implementing object with register_graphql_field() wp-graphql/wp-graphql#3096 would make sure things don't break downstream.

#115 (comment)

How

Testing Instructions

Additional Info

Checklist:

• My code is tested to the best of my abilities.
• My code follows the WordPress Coding Standards.
• My code has proper inline documentation.
• I have added unit tests to verify the code works as intended.
• The changes in this PR have been noted in CHANGELOG.md

[Copilot]

Pull Request Overview

This PR addresses type conflicts in WooGraphQL v0.21.1+ by updating the changelog entry.

• Added a changelog entry to document the fix for Product interface conflicts.

Files not reviewed (1)

• src/Extensions/WPGraphQLWooCommerce/Type/WPObject/SeoObjects.php: Language not supported