Add username suggestion when taken

public/language/sc/error.json

@@ -31,7 +31,7 @@
     "invalid-path": "Invalid path",
     "folder-exists": "Folder exists",
     "invalid-pagination-value": "Invalid pagination value, must be at least %1 and at most %2",
-    "username-taken": "Username taken",
+    "username-taken": "Username taken, try: %1",
     "email-taken": "Email taken",
     "email-nochange": "The email entered is the same as the email already on file.",
     "email-invited": "Email was already invited",
@@ -221,4 +221,4 @@
     "api.500": "An unexpected error was encountered while attempting to service your request.",
     "api.501": "The route you are trying to call is not implemented yet, please try again tomorrow",
     "api.503": "The route you are trying to call is not currently available due to a server configuration"
-}
+}

src/user/approval.js

@@ -39,7 +39,7 @@ module.exports = function (User) {
         await User.isDataValid(userData);
         const usernames = await db.getSortedSetRange('registration:queue', 0, -1);
         if (usernames.includes(userData.username)) {
-            throw new Error('[[error:username-taken]]');
+            throw new Error('[[error:username-taken, ${userData.username + "1"}]]');
         }
         const keys = usernames.filter(Boolean).map(username => `registration:queue:name:${username}`);
         const data = await db.getObjectsFields(keys, ['email']);