[SECURITY] Notify users about account security changes

- Currently if the password, primary mail, TOTP or security keys are
changed, no notification is made of that and makes compromising an
account a bit easier as it's essentially undetectable until the original
person tries to log in. Although other changes should be made as
well (re-authing before allowing a password change), this should go a
long way of improving the account security in Forgejo.
- Adds a mail notification for password and primary mail changes. For
the primary mail change, a mail notification is sent to the old primary
mail.
- Add a mail notification when TOTP or a security keys is removed, if no
other 2FA method is configured the mail will also contain that 2FA is
no longer needed to log into their account.
- `MakeEmailAddressPrimary` is refactored to the user service package,
as it now involves calling the mailer service.
- Unit tests added.
- Integration tests added.

services/mailer/mail_auth_test.go

@@ -0,0 +1,60 @@
+// Copyright 2024 The Forgejo Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package mailer_test
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/models/unittest"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/optional"
+	"code.gitea.io/gitea/modules/translation"
+	"code.gitea.io/gitea/services/mailer"
+	user_service "code.gitea.io/gitea/services/user"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestPasswordChangeMail(t *testing.T) {
+	defer require.NoError(t, unittest.PrepareTestDatabase())
+
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+	called := false
+	defer mailer.MockMailSettings(func(msgs ...*mailer.Message) {
+		assert.Len(t, msgs, 1)
+		assert.Equal(t, user.EmailTo(), msgs[0].To)
+		assert.EqualValues(t, translation.NewLocale("en-US").Tr("mail.password_change.subject"), msgs[0].Subject)
+		mailer.AssertTranslatedLocale(t, msgs[0].Body, "mail.password_change.text_1", "mail.password_change.text_2", "mail.password_change.text_3")
+		called = true
+	})()
+
+	require.NoError(t, user_service.UpdateAuth(db.DefaultContext, user, &user_service.UpdateAuthOptions{Password: optional.Some("NewPasswordYolo!")}))
+	assert.True(t, called)
+}
+
+func TestPrimaryMailChange(t *testing.T) {
+	defer require.NoError(t, unittest.PrepareTestDatabase())
+
+	user := unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: 2})
+	firstEmail := unittest.AssertExistsAndLoadBean(t, &user_model.EmailAddress{ID: 3, UID: user.ID, IsPrimary: true})
+	secondEmail := unittest.AssertExistsAndLoadBean(t, &user_model.EmailAddress{ID: 35, UID: user.ID}, "is_primary = false")
+
+	called := false
+	defer mailer.MockMailSettings(func(msgs ...*mailer.Message) {
+		assert.False(t, called)
+		assert.Len(t, msgs, 1)
+		assert.Equal(t, user.EmailTo(firstEmail.Email), msgs[0].To)
+		assert.EqualValues(t, translation.NewLocale("en-US").Tr("mail.primary_mail_change.subject"), msgs[0].Subject)
+		assert.Contains(t, msgs[0].Body, secondEmail.Email)
+		mailer.AssertTranslatedLocale(t, msgs[0].Body, "mail.primary_mail_change.text_1", "mail.primary_mail_change.text_2", "mail.primary_mail_change.text_3")
+		called = true
+	})()
+
+	require.NoError(t, user_service.MakeEmailAddressPrimary(db.DefaultContext, user, secondEmail, true))
+	assert.True(t, called)
+
+	require.NoError(t, user_service.MakeEmailAddressPrimary(db.DefaultContext, user, firstEmail, false))
+}