I'm a little confused what you want to do. You shouldn't need to do any kind of mapping or storing of that code yourself. Cognito will handle that.

Once you have that code you can exchange it with Cognito for an id_token. The code that does this will be in your Angular application (the redirect_url).

Are you familiar with the OAuth flow? Using the "Hosted UI" in Cognito is a nice way to get familiar with the flow