[GITEA] notifies admins on new user registration

Sends email with information on the new user (time of creation and time of last sign-in) and a link to manage the new user from the admin panel

closes: https://codeberg.org/forgejo/forgejo/issues/480

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/1371
Co-authored-by: Aravinth Manivannan <realaravinth@batsense.net>
Co-committed-by: Aravinth Manivannan <realaravinth@batsense.net>
(cherry picked from commit c721aa828b)
(cherry picked from commit 6487efcb9d)

Conflicts:
	modules/notification/base/notifier.go
	modules/notification/base/null.go
	modules/notification/notification.go
	https://codeberg.org/forgejo/forgejo/pulls/1422
(cherry picked from commit 7ea66ee1c5)

Conflicts:
	services/notify/notifier.go
	services/notify/notify.go
	services/notify/null.go
	https://codeberg.org/forgejo/forgejo/pulls/1469
(cherry picked from commit 7d2d997011)

services/mailer/mail_admin_new_user_test.go

@@ -0,0 +1,88 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package mailer
+
+import (
+	"context"
+	"strconv"
+	"strings"
+	"testing"
+
+	"code.gitea.io/gitea/models/db"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/setting"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func getTestUsers() []*user_model.User {
+	admin := new(user_model.User)
+	admin.Name = "admin"
+	admin.IsAdmin = true
+	admin.Language = "en_US"
+	admin.Email = "admin@forgejo.org"
+
+	newUser := new(user_model.User)
+	newUser.Name = "new_user"
+	newUser.Language = "en_US"
+	newUser.IsAdmin = false
+	newUser.Email = "new_user@forgejo.org"
+	newUser.LastLoginUnix = 1693648327
+	newUser.CreatedUnix = 1693648027
+
+	user_model.CreateUser(db.DefaultContext, admin)
+	user_model.CreateUser(db.DefaultContext, newUser)
+
+	users := make([]*user_model.User, 0)
+	users = append(users, admin)
+	users = append(users, newUser)
+
+	return users
+}
+
+func cleanUpUsers(ctx context.Context, users []*user_model.User) {
+	for _, u := range users {
+		db.DeleteByID(ctx, u.ID, new(user_model.User))
+	}
+}
+
+func TestAdminNotificationMail_test(t *testing.T) {
+	mailService := setting.Mailer{
+		From:     "test@forgejo.org",
+		Protocol: "dummy",
+	}
+
+	setting.MailService = &mailService
+	setting.Domain = "localhost"
+	setting.AppSubURL = "http://localhost"
+
+	// test with NOTIFY_NEW_SIGNUPS enabled
+	setting.Admin.NotifyNewSignUps = true
+
+	ctx := context.Background()
+	NewContext(ctx)
+
+	users := getTestUsers()
+	oldSendAsyncs := sa
+	defer func() {
+		sa = oldSendAsyncs
+		cleanUpUsers(ctx, users)
+	}()
+
+	sa = func(msgs []*Message) {
+		assert.Equal(t, len(msgs), 1, "Test provides only one admin user, so only one email must be sent")
+		assert.Equal(t, msgs[0].To, users[0].Email, "checks if the recipient is the admin of the instance")
+		manageUserURL := "/admin/users/" + strconv.FormatInt(users[1].ID, 10)
+		assert.True(t, strings.ContainsAny(msgs[0].Body, manageUserURL), "checks if the message contains the link to manage the newly created user from the admin panel")
+	}
+	MailNewUser(ctx, users[1])
+
+	// test with NOTIFY_NEW_SIGNUPS disabled; emails shouldn't be sent
+	setting.Admin.NotifyNewSignUps = false
+	sa = func(msgs []*Message) {
+		assert.Equal(t, 1, 0, "this shouldn't execute. MailNewUser must exit early since NOTIFY_NEW_SIGNUPS is disabled")
+	}
+
+	MailNewUser(ctx, users[1])
+}