Add Notifications section in User Settings (#35008)

Related: #34982

---------

Signed-off-by: NorthRealm <155140859+NorthRealm@users.noreply.github.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/user/setting/notifications.go

@@ -0,0 +1,62 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package setting
+
+import (
+	"errors"
+	"net/http"
+
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/optional"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/templates"
+	"code.gitea.io/gitea/services/context"
+	"code.gitea.io/gitea/services/user"
+)
+
+const tplSettingsNotifications templates.TplName = "user/settings/notifications"
+
+// Notifications render user's notifications settings
+func Notifications(ctx *context.Context) {
+	if !setting.Service.EnableNotifyMail {
+		ctx.NotFound(nil)
+		return
+	}
+
+	ctx.Data["Title"] = ctx.Tr("notifications")
+	ctx.Data["PageIsSettingsNotifications"] = true
+	ctx.Data["EmailNotificationsPreference"] = ctx.Doer.EmailNotificationsPreference
+
+	ctx.HTML(http.StatusOK, tplSettingsNotifications)
+}
+
+// NotificationsEmailPost set user's email notification preference
+func NotificationsEmailPost(ctx *context.Context) {
+	if !setting.Service.EnableNotifyMail {
+		ctx.NotFound(nil)
+		return
+	}
+
+	preference := ctx.FormString("preference")
+	if !(preference == user_model.EmailNotificationsEnabled ||
+		preference == user_model.EmailNotificationsOnMention ||
+		preference == user_model.EmailNotificationsDisabled ||
+		preference == user_model.EmailNotificationsAndYourOwn) {
+		log.Error("Email notifications preference change returned unrecognized option %s: %s", preference, ctx.Doer.Name)
+		ctx.ServerError("SetEmailPreference", errors.New("option unrecognized"))
+		return
+	}
+	opts := &user.UpdateOptions{
+		EmailNotificationsPreference: optional.Some(preference),
+	}
+	if err := user.UpdateUser(ctx, ctx.Doer, opts); err != nil {
+		log.Error("Set Email Notifications failed: %v", err)
+		ctx.ServerError("UpdateUser", err)
+		return
+	}
+	log.Trace("Email notifications preference made %s: %s", preference, ctx.Doer.Name)
+	ctx.Flash.Success(ctx.Tr("settings.email_preference_set_success"))
+	ctx.Redirect(setting.AppSubURL + "/user/settings/notifications")
+}