Identify user based on the JWT attached with request

Yes, your user ID is inside the JWT. So simply use a JWT decoder, there’s an NPM package for that.

For every request you just send in the JWT token along and do this:

const jwt_decode = require("jwt-decode"); //npmpackage

        let decoded = jwt_decode(data.token); //data is what you sent in.
        const userId = decoded.id;
        let user = await strapi.plugins["users-permissions"].services.user.fetch({
          id: userId,
        });