feat: adds surcharges property and model to Rate object

[Justintime50]

Description

Testing

Pull Request Type

Please select the option(s) that are relevant to this PR.

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Improvement (fixing a typo, updating readme, renaming a variable name, etc)