Fix API leaking Usermail if not logged in (#25097)

The API should only return the real Mail of a User, if the caller is
logged in. The check do to this don't work. This PR fixes this. This not
really a security issue, but can lead to Spam.

---------

Co-authored-by: silverwind <me@silverwind.io>

tests/integration/api_user_search_test.go

@@ -4,14 +4,12 @@
 package integration
 
 import (
-	"fmt"
 	"net/http"
 	"testing"
 
 	auth_model "code.gitea.io/gitea/models/auth"
 	"code.gitea.io/gitea/models/unittest"
 	user_model "code.gitea.io/gitea/models/user"
-	"code.gitea.io/gitea/modules/setting"
 	api "code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/tests"
 
@@ -54,11 +52,7 @@ func TestAPIUserSearchNotLoggedIn(t *testing.T) {
 	for _, user := range results.Data {
 		assert.Contains(t, user.UserName, query)
 		modelUser = unittest.AssertExistsAndLoadBean(t, &user_model.User{ID: user.ID})
-		if modelUser.KeepEmailPrivate {
-			assert.EqualValues(t, fmt.Sprintf("%s@%s", modelUser.LowerName, setting.Service.NoReplyAddress), user.Email)
-		} else {
-			assert.EqualValues(t, modelUser.Email, user.Email)
-		}
+		assert.EqualValues(t, modelUser.GetPlaceholderEmail(), user.Email)
 	}
 }