* bug: Use DSSE media types for artifactType
* Don't serialize DSSE extension if not present
* Update pkg/attestation/types.go
Co-authored-by: Joel Kamp <joel.kamp@docker.com>
* Don't error on no referrers
---------
Co-authored-by: Joel Kamp <joel.kamp@docker.com>
* Single attestation when creating VSA
* Create single layer images for referrers attestations
* Move mock to test package. Add artifacts test
* Add test for envelope detection
* Add tests for image/index saving
* Add mirror tests
* Remove AttestationImage field from AttestationManifest
* Update naming. strictReferers != laxReferrers
* Add specific test for SaveReferrers
* Use receivers for manifest functions
* Move SaveImage/SaveIndex from image-signing-verifier
* Ignore test fixtures in coverage
* Add AddImagesToIndex function
