How to add custom claims to JWTs

The text discusses the use of JSON Web Tokens (JWTs) to convey user identity and authorization details in a secure manner. JWTs package user information into a compact token that can be easily verified and used across services, enabling API routes to decode and use claims without extra queries. In an e-commerce scenario, a JWT can contain essential details such as user ID, roles, permissions, and additional information like membership level or last login time. A Node.js snippet using the `jsonwebtoken` library is provided to generate a JWT with custom claims, including security best practices such as setting expirations, validating issuers and audiences, and avoiding sensitive information storage. The resulting JWT encapsulates user identity and access details, making them easily accessible in API routes.