Allow options to disable user deletion from the interface on app.ini (#29275)

Extract from #20549

This PR added a new option on app.ini `[admin]USER_DISABLED_FEATURES` to
allow the site administrator to disable users visiting deletion user
interface or allow.
This options are also potentially allowed to define more features in
future PRs.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

custom/conf/app.example.ini

 ;;
 ;; Default configuration for email notifications for users (user configurable). Options: enabled, onmention, disabled
 ;DEFAULT_EMAIL_NOTIFICATIONS = enabled
+;; Disabled features for users, could be "deletion", more features can be disabled in future
+;; - deletion: a user cannot delete their own account
+;USER_DISABLED_FEATURES =
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

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

 
 - `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.
+- `USER_DISABLED_FEATURES`: **_empty_** Disabled features for users, could be `deletion` and more features can be added in future.
+  - `deletion`: User cannot delete their own account.
 
 ## Security (`security`)
 

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

 
 - `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`， 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。
 
 ## 安全性 (`security`)
 

modules/setting/admin.go

 
 package setting
 
+import "code.gitea.io/gitea/modules/container"
+
 // Admin settings
 var Admin struct {
 	DisableRegularOrgCreation bool
 	DefaultEmailNotification  string
+	UserDisabledFeatures      container.Set[string]
 }
 
 func loadAdminFrom(rootCfg ConfigProvider) {
-	mustMapSetting(rootCfg, "admin", &Admin)
 	sec := rootCfg.Section("admin")
+	Admin.DisableRegularOrgCreation = sec.Key("DISABLE_REGULAR_ORG_CREATION").MustBool(false)
 	Admin.DefaultEmailNotification = sec.Key("DEFAULT_EMAIL_NOTIFICATIONS").MustString("enabled")
+	Admin.UserDisabledFeatures = container.SetOf(sec.Key("USER_DISABLED_FEATURES").Strings(",")...)
 }
+
+const (
+	UserFeatureDeletion = "deletion"
+)

routers/web/user/setting/account.go

 
 // DeleteAccount render user suicide page and response for delete user himself
 func DeleteAccount(ctx *context.Context) {
+	if setting.Admin.UserDisabledFeatures.Contains(setting.UserFeatureDeletion) {
+		ctx.Error(http.StatusNotFound)
+		return
+	}
+
 	ctx.Data["Title"] = ctx.Tr("settings")
 	ctx.Data["PageIsSettingsAccount"] = true
 
 	ctx.Data["EmailNotificationsPreference"] = ctx.Doer.EmailNotificationsPreference
 	ctx.Data["ActivationsPending"] = pendingActivation
 	ctx.Data["CanAddEmails"] = !pendingActivation || !setting.Service.RegisterEmailConfirm
+	ctx.Data["UserDisabledFeatures"] = &setting.Admin.UserDisabledFeatures
 
 	if setting.Service.UserDeleteWithCommentsMaxTime != 0 {
 		ctx.Data["UserDeleteWithCommentsMaxTime"] = setting.Service.UserDeleteWithCommentsMaxTime.String()

templates/user/settings/account.tmpl

 			{{end}}
 		</div>
 
+		{{if not ($.UserDisabledFeatures.Contains "deletion")}}
 		<h4 class="ui top attached error header">
 			{{ctx.Locale.Tr "settings.delete_account"}}
 		</h4>
 					</button>
 				</div>
 			</form>
+			<div class="ui g-modal-confirm delete modal" id="delete-account">
+				<div class="header">
+					{{svg "octicon-trash"}}
+					{{ctx.Locale.Tr "settings.delete_account_title"}}
+				</div>
+				<div class="content">
+					<p>{{ctx.Locale.Tr "settings.delete_account_desc"}}</p>
+				</div>
+				{{template "base/modal_actions_confirm" .}}
+			</div>
 		</div>
+		{{end}}
 	</div>
 
 <div class="ui g-modal-confirm delete modal" id="delete-email">
 	{{template "base/modal_actions_confirm" .}}
 </div>
 
-<div class="ui g-modal-confirm delete modal" id="delete-account">
-	<div class="header">
-		{{svg "octicon-trash"}}
-		{{ctx.Locale.Tr "settings.delete_account_title"}}
-	</div>
-	<div class="content">
-		<p>{{ctx.Locale.Tr "settings.delete_account_desc"}}</p>
-	</div>
-	{{template "base/modal_actions_confirm" .}}
-</div>
-
 {{template "user/settings/layout_footer" .}}