Add user blocking

- Add the ability to block a user via their profile page.
- This will unstar their repositories and visa versa.
- Blocked users cannot create issues or pull requests on your the doer's repositories (mind that this is not the case for organizations).
- Blocked users cannot comment on the doer's opened issues or pull requests.
- Blocked users cannot add reactions to doer's comments.
- Blocked users cannot cause a notification trough mentioning the doer.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/540

models/forgejo_migrations/v1_20/v1.go

@@ -0,0 +1,21 @@
+// Copyright 2023 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package forgejo_v1_20 //nolint:revive
+
+import (
+	"code.gitea.io/gitea/modules/timeutil"
+
+	"xorm.io/xorm"
+)
+
+func AddForgejoBlockedUser(x *xorm.Engine) error {
+	type ForgejoBlockedUser struct {
+		ID          int64              `xorm:"pk autoincr"`
+		BlockID     int64              `xorm:"index"`
+		UserID      int64              `xorm:"index"`
+		CreatedUnix timeutil.TimeStamp `xorm:"created"`
+	}
+
+	return x.Sync(new(ForgejoBlockedUser))
+}