Support custom parameters with Authorization Code and Refresh Token grant

[frederikprijck]

Changes

Authorization Code (with and without PKCE) and Refresh Token Grants should accept custom parameters.

Testing

Please describe how this can be tested by reviewers. Be specific about anything not tested and reasons why. If this library has unit and/or integration testing, tests should be added for new functionality and existing tests should complete without errors.

• [x] This change adds unit test coverage
• [x] This change adds integration test coverage

Checklist

• [x] I have read the Auth0 general contribution guidelines
• [x] I have read the Auth0 Code of Conduct
• [x] All existing and new tests complete without errors