@Override
    public String toString() {
        return MoreObjects.toStringHelper(this)
                          .add("entityId", entityId)
                          .add("signingCredential", signingCredential)
                          .add("encryptionCredential", encryptionCredential)
                          .add("ssoEndpoint", ssoEndpoint)
                          .add("sloReqEndpoint", sloReqEndpoint)
                          .add("sloResEndpoint", sloResEndpoint)
                          .add("acsEndpoint", acsEndpoint)
                          .add("nameIdPolicy", nameIdPolicy)
                          .toString();
    }
Returns a {@link NameIDPolicy} of the service provider which is sent to the identity provider via
an authentication request.
saml/src/main/java/com/linecorp/armeria/server/saml/SamlIdentityProviderConfig.java