Hi! So, I think this PR is too big to be reviewed. To make the review process more effective, let's divide it.
For this case, let me help you. I've already divided your changes into a stacked PR.

1. [PART 1] Ref/categories to tags  #3 -> Server
2. [PART 2] Ref/categories to tags p2 #4 -> Server
3. [PART 3] Ref/categories to tags p3 #5 -> Client
4. [PART4] Ref/categories to tags p4 #6 -> Client
5. [PART 5] Ref/categories to tags p5 #7 -> Client

I also prefilled the description with the what, why, and how template for you. But, please do modify the description if I make a mistake. A good description may ease other developers who read the PR in the future.

Let's check those PRs one by one. You can merge PR part 5 to part 4, then merge part 4 to part 3, and so on. After that we gonna have all changes that you have created in PR part 1. Lastly, you can merge PR part 1 into the master.

Cheers!