Introduce <ArrayInputBase>, <SimpleFomIteratorBase> and <SimpleFormIteratorItemBase>

[djhi]

Problem

When implementing new UI (e.g. ShadnAdminKit), we have to repeat a lot of code that could be in ra-core.

Solution

Introduce <ArrayInputBase>, <SimpleFomIteratorBase> and <SimpleFormIteratorItemBase>

How To Test

• All tests should pass
• All stories should behave as before

Additional Checks

• The PR targets master for a bugfix or a documentation fix, or next for a feature
• The PR includes unit tests (if not possible, describe why)
• The PR includes one or several stories (if not possible, describe why)
• The documentation is up to date

Also, please make sure to read the contributing guidelines.

[Copilot]

Pull Request Overview

This PR introduces three new base components (<ArrayInputBase>, <SimpleFormIteratorBase>, and <SimpleFormIteratorItemBase>) to facilitate code reuse when implementing custom UI libraries. These components extract the core logic from existing UI-specific components to ra-core, enabling developers to build new UI implementations without duplicating business logic.

• Introduces new base components in ra-core for ArrayInput and SimpleFormIterator functionality
• Refactors existing Material-UI components to use the new base components
• Adds comprehensive test-ui components for testing the new functionality

Reviewed Changes

Copilot reviewed 32 out of 32 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/ra-core/src/controller/input/ArrayInputBase.tsx	New base component for array input functionality
packages/ra-core/src/controller/input/SimpleFormIteratorBase.tsx	New base component for form iterator logic
packages/ra-core/src/controller/input/SimpleFormIteratorItemBase.tsx	New base component for iterator item functionality
packages/ra-ui-materialui/src/input/ArrayInput/ArrayInput.tsx	Refactored to use ArrayInputBase
packages/ra-ui-materialui/src/input/ArrayInput/SimpleFormIterator.tsx	Refactored to use SimpleFormIteratorBase
packages/ra-ui-materialui/src/input/ArrayInput/SimpleFormIteratorItem.tsx	Refactored to use SimpleFormIteratorItemBase
packages/ra-core/src/test-ui/*	New test UI components for testing base components
docs_headless/src/content/docs/ArrayInputBase.md	Documentation for new ArrayInputBase component

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}