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>

models/migrations/migrations.go

@@ -560,6 +560,8 @@ var migrations = []Migration{
 	NewMigration("Add support for SHA256 git repositories", v1_22.AdjustDBForSha256),
 	// v287 -> v288
 	NewMigration("Use Slug instead of ID for Badges", v1_22.UseSlugInsteadOfIDForBadges),
+	// v288 -> v289
+	NewMigration("Add user_blocking table", v1_22.AddUserBlockingTable),
 }
 
 // GetCurrentDBVersion returns the current db version

models/migrations/v1_22/v288.go

@@ -0,0 +1,26 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_22 //nolint
+
+import (
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"xorm.io/xorm"
+)
+
+type Blocking struct {
+	ID          int64 `xorm:"pk autoincr"`
+	BlockerID   int64 `xorm:"UNIQUE(block)"`
+	BlockeeID   int64 `xorm:"UNIQUE(block)"`
+	Note        string
+	CreatedUnix timeutil.TimeStamp `xorm:"INDEX created"`
+}
+
+func (*Blocking) TableName() string {
+	return "user_blocking"
+}
+
+func AddUserBlockingTable(x *xorm.Engine) error {
+	return x.Sync(&Blocking{})
+}