Fix: Add identity parameter to options in token generation

[sddion]

I encountered an error where the identity parameter was required but not specified in the options during token generation. This resulted in a failure to create a new AccessToken instance.

Changes Made

• Added the identity parameter to the options in the token generation process.
• Ensured that the identity parameter is properly passed to the AccessToken constructor.

Error Details

Error: identity is required to be specified in options
    at new AccessToken (/home/dion/Desktop/voice-javascript-sdk-quickstart-node/node_modules/twilio/lib/jwt/AccessToken.js:28:19)
    at tokenGenerator (/home/dion/Desktop/voice-javascript-sdk-quickstart-node/src/handler.js:13:23)
    at /home/dion/Desktop/voice-javascript-sdk-quickstart-node/src/router.js:7:12
    at Layer.handle [as handle_request] (/home/dion/Desktop/voice-javascript-sdk-quickstart-node/node_modules/express/lib/router/layer.js:95:5)
    at next (/home/dion/Desktop/voice-javascript-sdk-quickstart-node/node_modules/express/lib/router/route.js:149:13)
    at Route.dispatch (/home/dion/Desktop/voice-javascript-sdk-quickstart-node/node_modules/express/lib/router/route.js:119:3)
    at Layer.handle [as handle_request] (/home/dion/Desktop/voice-javascript-sdk-quickstart-node/node_modules/express/lib/router/layer.js:95:5)
    at /home/dion/Desktop/voice-javascript-sdk-quickstart-node/node_modules/express/lib/router/index.js:284:15
    at Function.process_params (/home/dion/Desktop/voice-javascript-sdk-quickstart-node/node_modules/express/lib/router/index.js:346:12)
    at next (/home/dion/Desktop/voice-javascript-sdk-quickstart-node/node_modules/express/lib/router/index.js:280:10)

Testing

• Tested the fix locally to ensure that the error no longer occurs.
• Added unit tests to cover the fix and prevent regressions.