Describe the bug

Cedarling cannot find the TrustedIssuer entity if multiple were defined in the policy store.

To Reproduce
Steps to reproduce the behavior:

1. Have a Workload or User entity that needs an iss attribute of type TrustedIssuer
2. Have 2 or more trusted issuers defined in the policy store.
3. Try any authorization check

Expected behavior

Entity creation should not fail due to a missing iss.