How do I handle access token in a plug-in that provides login capabilities?

I am developing a plug-in that brings data from an external server to an unreal engine. To authenticate users, access token can be imported through the http communication function provided by the Unreal Engine through API, which has already been developed in the backend server. However, information containing access tokens should be handled safely. As soon as the access token is answered, it should be stored in a safe space, or a server should be built for each plug-in and stored on the server, etc. It should be implemented to store the access token safely. How do I implement plug-ins that implement these features?