Add ETH Key Support to Gateway Services

[p5150j]

Description

Extend our gateway services to support Ethereum keys and signatures, using the newly created library.

Tasks

• Identify all gateway services requiring updates
• Implement ETH key validation in API endpoints
• Update authentication mechanisms to support ETH signatures
• Add support for ETH address formats
• Modify request/response handling for ETH compatibility
• Create tests for new functionality

Acceptance Criteria

• [ ] All gateway services accept ETH-format keys
• [ ] Authentication works with ETH signatures
• [ ] APIs properly handle ETH addresses in requests and responses
• [ ] Backward compatibility maintained for existing keys
• [ ] Load testing shows no performance degradation
• [ ] All new code has appropriate test coverage
• [ ] Documentation updated to reflect new capabilities