Core/Commands: Prevent creating accounts containing '@' character with .account create command

src/server/scripts/Commands/cs_account.cpp

@@ -121,6 +121,13 @@ public:
         if (!accountName || !password)
             return false;
 
+        if (strchr(accountName, '@'))
+        {
+            handler->PSendSysMessage(LANG_ACCOUNT_USE_BNET_COMMANDS);
+            handler->SetSentErrorMessage(true);
+            return false;
+        }
+
         switch (sAccountMgr->CreateAccount(std::string(accountName), std::string(password), email))
         {
             case AccountOpResult::AOR_OK: