sent invite check pre username if exists

public/takeinvite.php

@@ -35,8 +35,14 @@ $body = str_replace("<br />", "<br />", nl2br(trim(strip_tags($_POST["body"]))))
 if(!$body)
 	bark($lang_takeinvite['std_must_enter_personal_message']);
 
-if ($isPreRegisterEmailAndUsername && empty($preRegisterUsername)) {
-    bark(nexus_trans("invite.require_pre_register_username"));
+if ($isPreRegisterEmailAndUsername) {
+    if (empty($preRegisterUsername)) {
+        bark(nexus_trans("invite.require_pre_register_username"));
+    }
+    $exists = \App\Models\User::query()->where('username', $preRegisterUsername)->exists();
+    if ($exists) {
+        bark(nexus_trans("user.username_already_exists", ["username" => $preRegisterUsername]));
+    }
 }
 
 

resources/lang/en/user.php

@@ -54,4 +54,5 @@ return [
             'body' => 'You had been :action to :new_class, administrator: :operator, reason: :reason.',
         ],
     ],
+    'username_already_exists' => 'Username::username already exists',
 ];

resources/lang/zh_CN/user.php

@@ -54,4 +54,5 @@ return [
             'body' => '你被:action为:new_class，管理员：:operator, 原因：:reason。',
         ],
     ],
+    'username_already_exists' => '用户名：:username 已经存在',
 ];

resources/lang/zh_TW/user.php

@@ -54,4 +54,5 @@ return [
             'body' => '你被:action為:new_class，管理員：:operator, 原因：:reason。',
         ],
     ],
+    'username_already_exists' => '用戶名：:username 已經存在',
 ];