public SamlServiceProviderBuilder signatureAlgorithm(String signatureAlgorithm) {
        this.signatureAlgorithm = requireNonNull(signatureAlgorithm, "signatureAlgorithm");
        return this;
    }
Sets a signature algorithm which is used for signing by this service provider.
saml/src/main/java/com/linecorp/armeria/server/saml/SamlServiceProviderBuilder.java