fix: [FIND-070] _replaceTokenHolder Zero-Index Corruption

[jaime-iobermudez]

This pull request adds an important audit fix to the ERC1410 token holder management logic by ensuring that replaceTokenHolder correctly checks for the existence of the old token holder before attempting replacement. It also introduces a mock contract to facilitate direct testing of internal storage wrapper functions and adds comprehensive tests to verify the new guard logic.

Audit fix and testing improvements:

• Added a guard in ERC1410StorageWrapper.replaceTokenHolder to revert with TokenHolderNotFound if the oldTokenHolder does not exist (i.e., its index is zero), preventing accidental corruption of the token holder registry.
• Introduced the TokenHolderNotFound custom error to the IERC1410Types interface for clearer revert reasons.

Testing infrastructure:

• Created MockERC1410StorageWrapper, a test-only contract that exposes internal functions of ERC1410StorageWrapper for direct unit testing, bypassing the diamond infrastructure.
• Updated integration tests in SecurityHolders.test.ts to use the new mock contract and added tests that verify the new existence guard in replaceTokenHolder, including cases where the holder was never registered or was removed. [1] [2]

Type of change

• Bug fix 🐞
• New feature ✨
• Breaking change 💥
• Documentation update 📖
• Refactor 🔧

Testing

Node version:

• 20
• 22
• 24

Checklist

• Style Guidelines followed ✅
• Documentation Updated 📚
• Linters - No New Warnings ⚠️
• Local Tests Pass ✅
• Effective Tests Added ✔️
• No reduction of Coverage ✅