Add user blocking (#29028)

Fixes #17453

This PR adds the abbility to block a user from a personal account or
organization to restrict how the blocked user can interact with the
blocker. The docs explain what's the consequence of blocking a user.

Screenshots:


![grafik](https://github.com/go-gitea/gitea/assets/1666336/4ed884f3-e06a-4862-afd3-3b8aa2488dc6)


![grafik](https://github.com/go-gitea/gitea/assets/1666336/ae6d4981-f252-4f50-a429-04f0f9f1cdf1)


![grafik](https://github.com/go-gitea/gitea/assets/1666336/ca153599-5b0f-4b4a-90fe-18bdfd6f0b6b)

---------

Co-authored-by: Lauris BH <lauris@nix.lv>

docs/content/usage/blocking-users.en-us.md

@@ -0,0 +1,56 @@
+---
+date: "2024-01-31T00:00:00+00:00"
+title: "Blocking a user"
+slug: "blocking-user"
+sidebar_position: 25
+toc: false
+draft: false
+aliases:
+  - /en-us/webhooks
+menu:
+  sidebar:
+    parent: "usage"
+    name: "Blocking a user"
+    sidebar_position: 30
+    identifier: "blocking-user"
+---
+
+# Blocking a user
+
+Gitea supports blocking of users to restrict how they can interact with you and your content.
+
+You can block a user in your account settings, from the user's profile or from comments created by the user.
+The user is not directly notified about the block, but they can notice they are blocked when they attempt to interact with you.
+Organization owners can block anyone who is not a member of the organization too.
+If a blocked user has admin permissions, they can still perform all actions even if blocked.
+
+### When you block a user
+
+- the user stops following you
+- you stop following the user
+- the user's stars are removed from your repositories
+- your stars are removed from their repositories
+- the user stops watching your repositories
+- you stop watching their repositories
+- the user's issue assignments are removed from your repositories
+- your issue assignments are removed from their repositories
+- the user is removed as a collaborator on your repositories
+- you are removed as a collaborator on their repositories
+- any pending repository transfers to or from the blocked user are canceled
+
+### When you block a user, the user cannot
+
+- follow you
+- watch your repositories
+- star your repositories
+- fork your repositories
+- transfer repositories to you
+- open issues or pull requests on your repositories
+- comment on issues or pull requests you've created
+- comment on issues or pull requests on your repositories
+- react to your comments on issues or pull requests
+- react to comments on issues or pull requests on your repositories
+- assign you to issues or pull requests
+- add you as a collaborator on their repositories
+- send you notifications by @mentioning your username
+- be added as team member (if blocked by an organization)