[feat]: Improve auth_controller.js file

[Yash-Vashishth]

Hi @ankit071105, your site is really great!! I just wanted to change some elements of (Ticket-Booking-main1/server/controllers/v1/auth_controller.js) file. so that it can:-

1. Contain JSDoc comments for better documentation.
2. Have consistent use of const for variable declarations.
3. Have used environment variables for JWT secret.
4. Improved error messages for clarity.
5. Centralized error handling through an asyncHandler.

I have a code ready for this. Could u pls assign me this issue so that I can make the necessary changes.
(Note- Please also add the hacktoberfest and gssoc-ext tags to the issue and also label it lvl 2 since I needed to identify each and every minute elementary changes and right them)

Thanks,
Yash Vashishth
(Contributor, GSSoC'24(Extd) and Hacktoberfes'24)

[github-actions]

👋 Thank you @Yash-Vashishth for raising an issue! We appreciate your effort in helping us improve. Our team will review it shortly. Stay tuned!