[Request] Provide docs for SAML signing and encryption with OneLogin for better security

[seieric]

Hi, I found this wonderful plugin in the plugin directory and I have configured the plugin via hook.

However, during the configuration, I realized this plugin does not have documentation for SAML signing and encryption with One Login. I finally found that I can configure signing and encryption by putting advanced parameters in advanced_settings_example.php to internal_config.

I think this trick should be widely known so that every user can configure SAML in more secure way.
I would be grateful if you add documentation for them in README or somewhere.

Thank you!