docs: private ObjectMetadata toObjectMetadataEO(ObjectMetadata metadata) {
          // If we generated a symmetric key to encrypt the data, store it in the
          // object metadata.
          byte[] encryptedCEK = getEncryptedCEK();
          metadata.addUserMetadata(Headers.CRYPTO_KEY,
                                   Base64.encodeAsString(encryptedCEK));
          // Put the cipher initialization vector (IV) into the object metadata
          byte[] iv = cipherLite.getIV();
          metadata.addUserMetadata(Headers.CRYPTO_IV, Base64.encodeAsString(iv));
          // Put the materials description into the object metadata as JSON
          metadata.addUserMetadata(Headers.MATERIALS_DESCRIPTION,
                                   kekMaterialDescAsJson());
          return metadata;
      }