[ @connection_name ] - VARCHAR with an existing Dynamics 365 connection name;
A value has to reference Dynamics 365 aware service which you are going to authorize your Azure application for.
[ @callback_url ] - VARCHAR; The URL the user will be redirected to after authorizing your application.
[ @state ] - NVARCHAR; this field indicates any state that may be useful to your application upon receipt of the response. Your application receives the same value it sent, as this parameter makes a round-trip to Dynamics authorization server and back. Uses include redirecting the user to the correct resource in your site, using nonces, and mitigating cross-site request forgery.