start pulling in the github api client wrapper

Signed-off-by: Meredith Lancaster <malancas@github.com>

pkg/cmd/attestation/github/attestation.go

@@ -0,0 +1,33 @@
+package github
+
+import (
+	"fmt"
+
+	"github.com/sigstore/sigstore-go/pkg/bundle"
+)
+
+const (
+	GetAttestationByRepoAndSubjectDigestPath  = "repos/%s/attestations/%s"
+	GetAttestationByOwnerAndSubjectDigestPath = "orgs/%s/attestations/%s"
+)
+
+type ErrNoAttestations struct {
+	name   string
+	digest string
+}
+
+func (e ErrNoAttestations) Error() string {
+	return fmt.Sprintf("no attestations found for digest %s in %s", e.name, e.digest)
+}
+
+func newErrNoAttestations(name, digest string) ErrNoAttestations {
+	return ErrNoAttestations{name, digest}
+}
+
+type Attestation struct {
+	Bundle *bundle.ProtobufBundle `json:"bundle"`
+}
+
+type AttestationsResponse struct {
+	Attestations []*Attestation `json:"attestations"`
+}