feat: Add amount to Signifyd

[adi-kmt]

Type of Change

• [ ] Bugfix
• [ ] New feature
• [x] Enhancement
• [ ] Refactoring
• [ ] Dependency updates
• [ ] Documentation
• [ ] CI/CD

This PR solves issue #6119

Description

Additional Changes

• [x] This PR modifies the API contract
• [ ] This PR modifies the database schema
• [ ] This PR modifies application configuration/environment variables

Motivation and Context

How did you test it?

Checklist

• [ ] I formatted the code cargo +nightly fmt --all
• [ ] I addressed lints thrown by cargo clippy
• [ ] I reviewed the submitted code
• [ ] I added unit tests for my changes where possible