f0a0dd6d73
- Add `signature_data` field to `ContractSigner` to store base64 encoded signature image data. Allows for storing visual signatures alongside electronic ones. - Implement `sign` method for `ContractSigner` to handle signing with optional signature data and comments. Improves the flexibility and expressiveness of the signing process. - Add Rhai functions for signature management, including signing with/without data and clearing signature data. Extends the Rhai scripting capabilities for contract management. - Add comprehensive unit tests to cover the new signature functionality. Ensures correctness and robustness of the implementation. - Update examples to demonstrate the new signature functionality. Provides clear usage examples for developers.