- Verification should be able to correctly validate a bundle as
  cryptographically valid (VerificationOptions.empty())
- Verifiers may also include signer identity during verification
- Verifiers should extract the embedded attestation to do further
  analysis on the attestation. Sigstore-java does not process
  those in any way
- There is no signing options for DSSE bundles

Signed-off-by: Appu Goundan <appu@google.com>