chore(tests): unit tests for Claim Cache

[fforbeck]

Test Cases

• should cache assert/location claims
• should return an error indicating missing capabilities
• should return an error indicating a failure in reading caveats
• should return an error when invalid data causes ContextID.ToEncoded() to fail
• should handle the expiration correctly and cache the claim
• should handle the absence of expiration correctly and cache the claim
• should handle a delegation with a range in the caveats and cache appropriately
• should handle a delegation without a range in the caveats and cache appropriately
• should propagate the error from the claims.Cache function
• should propagate the error from the provIndex.Cache function

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Files with missing lines	Coverage Δ
pkg/service/service.go	39.03% <100.00%> (+6.63%)	⬆️

... and 2 files with indirect coverage changes