URL of the identity provider’s authorization server. For OpenID Connect and OAuth 2.0, the auth_url is found in the provider’s documentation or, for OpenID Connect only, by looking for the authorization_endpoint entry in the website’s discovery document. For SAML 2 providers you can determine the URL by retrieving the provider’s SAML metadata and looking for the SingleSignOnService element and the Location attribute. Regardless, the auth_url value must use the HTTPS scheme. This member is used with OAuth, OpenID Connect, and SAML 2 providers.