public SamlIdentityProviderConfigBuilder encryptionKey(String encryptionKey) {
        this.encryptionKey = requireNonNull(encryptionKey, "encryptionKey");
        return this;
    }
Sets an {@code encryption} key name for an identity provider.
saml/src/main/java/com/linecorp/armeria/server/saml/SamlIdentityProviderConfigBuilder.java