Resolve Issue #247

[seconroy]

Description

Resolve issue #247, SIG Credentials requires both variable and constant values be sent in the payload as seen in the issue comment.

Types of Changes

• [ ] New feature (non-breaking change which adds functionality)
• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Build/CI change
• [ ] Code quality improvement/refactoring/documentation (no functional changes)

Checklist

• [x] My code follows the code style of this project
• [x] I have added tests to cover my changes
• [x] All new and existing tests pass locally