Caching Support

Hi,
Thank you for great boilerplate! How about adding support for caching in this to optimize the boilerplate more?
Nowadays it seems normal to provide caching out of the box.

Something like Redis with:

- Auth in Cache for storing SET of valid JWT token of a user and removing any blacklisted tokens from the SET.
- Storing user detail on Cache as well, and updating it value once user has been updated so that the JWT token with old user details can be avoided.

Thanks.

The issue names no files or tests; start by tracing the authentication/JWT and user-update flows in the Node.js/Express boilerplate and identify where Redis would fit. Define the cache invalidation behavior for blacklisted tokens and updated user details, then verify those cases with tests.

Written by the indexing model from the issue text.