add/remove to favorites for a user

[hparul]

Description

This PR should be able to add a product to favorites. Fixes https://github.com/HackYourFuture-CPH/fp-class19/issues/198

How to test?

Please provide a short summary how your changes can be tested? 1.first you need to log in to be able to add products to favorites. click on favorite symbol on a product and check users fav list on fav icon in header.

Checklist

• [x] I have performed a self-review of my own code
• [x] I have followed the name conventions for CSS Classnames and filenames, Components names and filenames, Style filenames, if you are in doubt check the the project README.MD and here https://github.com/HackYourFuture-CPH/curriculum/blob/master/review/review-checklist.md
• [x] I have commented my code, particularly in hard-to-understand areas, if you code was simple enough mark the box anyway
• [x] I have made corresponding changes to the documentation, if you code was simple enough mark the box anyway
• [x] This PR is ready to be merged and not breaking any other functionality