Allow options to disable user gpg keys configuration from the interface on app.ini (#29486)

Follow #29447
Fix #29454
Extract from #20549

(cherry picked from commit 9de5e39e25009bacc5ca201ed97e9cbb623e56e9)

Conflicts:
	custom/conf/app.example.ini
	docs/content/administration/config-cheat-sheet.en-us.md
	docs/content/administration/config-cheat-sheet.zh-cn.md
	trivial context conflict

docs/content/administration/config-cheat-sheet.en-us.md

@@ -518,7 +518,9 @@ And the following unique queues:
 
 - `DEFAULT_EMAIL_NOTIFICATIONS`: **enabled**: Default configuration for email notifications for users (user configurable). Options: enabled, onmention, disabled
 - `DISABLE_REGULAR_ORG_CREATION`: **false**: Disallow regular (non-admin) users from creating organizations.
-- `SEND_NOTIFICATION_EMAIL_ON_NEW_USER`: **false**: Send an email to all admins when a new user signs up to inform the admins about this act.
+- `USER_DISABLED_FEATURES`: **_empty_** Disabled features for users, could be `deletion`, `manage_gpg_keys` and more features can be added in future.
+  - `deletion`: User cannot delete their own account.
+  - `manage_gpg_keys`: User cannot configure gpg keys
 
 ## Security (`security`)
 

docs/content/administration/config-cheat-sheet.zh-cn.md

@@ -497,6 +497,9 @@ Gitea 创建以下非唯一队列：
 
 - `DEFAULT_EMAIL_NOTIFICATIONS`: **enabled**：用户电子邮件通知的默认配置（用户可配置）。选项：enabled、onmention、disabled
 - `DISABLE_REGULAR_ORG_CREATION`: **false**：禁止普通（非管理员）用户创建组织。
+- `USER_DISABLED_FEATURES`:**_empty_** 禁用的用户特性，当前允许为空或者 `deletion`，`manage_gpg_keys` 未来可以增加更多设置。
+  - `deletion`: 用户不能通过界面或者API删除他自己。
+  - `manage_gpg_keys`: 用户不能配置 GPG 密钥
 
 ## 安全性 (`security`)