Add Rekor body to TransparencyLogEntry

Signed-off-by: Cody Soyland <codysoyland@github.com>

protos/sigstore_rekor.proto

@@ -110,4 +110,11 @@ message TransparencyLogEntry {
         // entry was appended to the log, and that the log has not been
         // altered.
         InclusionProof inclusion_proof = 6;
+        // The canonicalized Rekor entry body, used for SET verification. This
+        // is the same as the body returned by Rekor. It's included here for
+        // cases where the client cannot deterministically reconstruct the
+        // bundle from the other fields. Clients MUST verify that the signature
+        // referenced in the canonicalized_body matches the signature provided
+        // in the bundle content.
+        bytes canonicalized_body = 7;
 }