private SamlIdentityProviderConfig resolveIdpConfig(Issuer issuer) {
        final String value = issuer.getValue();
        if (value != null) {
            final SamlIdentityProviderConfig config = idpConfigs.get(value);
            if (config != null) {
                return config;
            }
        }
        throw new InvalidSamlRequestException("failed to find identity provider from configuration: " +
                                              issuer.getValue());
    }
A service which receives an assertion from the remote identity provider.
saml/src/main/java/com/linecorp/armeria/server/saml/SamlAssertionConsumerFunction.java