I'm trying to authenticate with a OAuth2.0 service when my MessagesExtension app loads. I see that one of the parameters the service requires is a redirect_uri, which will pass back an authorization code to my application through the redirect callback. However, I'm unable to provide a redirect_uri that will invoke my application since MessagesExtension applications do not have an appDelegate. Is it just not possible to authenticate with services requiring a redirect_uri with a MessagesExtension application?