Fix #630: Product registration does not list all child categories

[MIbrahimPro]

PR Checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

When selecting a category in product registration (or when choosing a parent category in category edit), the admin category tree only shows a limited number of child categories per parent (capped by default collection size, e.g. 20). Parents with many children (e.g. 75) appear truncated: not all children are listed or selectable.

Issue Number: #630

What is the new behavior?

• Backend: For categories GraphQL queries that use only a parent filter (and no explicit page/limit), default pagination is no longer applied. All children for that parent are returned, so the tree can show the full list (e.g. all 75 children).
• Frontend: Category tree list items use stable React keys (categoryId instead of value) so rendering is consistent when many children are shown.
• Tests: New integration test categoryCollectionPagination.test.js asserts that parent-only category queries are not paginated, and that explicit page/limit still apply when provided.

Does this PR introduce a breaking change?

• Yes
• No

Other information

Fixes #630.
Manual check: expand a parent with many children in Admin → Products → New Product → Category, and in Admin → Category → Edit → Parent category; all children should appear.

[MIbrahimPro]

Hi,
what is going on