public SamlServiceProviderBuilder idpConfigSelector(
            SamlIdentityProviderConfigSelector idpConfigSelector) {
        this.idpConfigSelector = requireNonNull(idpConfigSelector, "idpConfigSelector");
        return this;
    }
Sets a {@link SamlIdentityProviderConfigSelector} which determines a suitable idp for a request.
saml/src/main/java/com/linecorp/armeria/server/saml/SamlServiceProviderBuilder.java