Comprehensive test coverage and upgradability

We provided the client and tested the code with a test suite that provides extensive coverage of the ExtendedERC20 contract, including

• Basic ERC-20 functionality

• KYC and blacklist features

• Minting, burning, and wiping tokens

• Pausing and unpausing transfers

• Role-based access control

• Document-hash registry

• Disabling/enabling KYC and blacklist features

• Batch role management

• Contract initialization and reinitialization prevention

While the client's tests focused primarily on blacklist functionality, we recommend that the client reproduces and expands upon these tests to ensure full coverage of all contract features.

Regarding upgradability, while we have included basic tests for the upgrade process, role preservation, and storage integrity, we strongly advise conducting more extensive upgradability testing.