Suggest a new username if a username is taken during registration #1
Description
NodeBB should automatically suggest an alternative username when the chosen username is already in use. At present, it simply displays the message 'Username taken.' Instead, we propose appending a suffix string to the user's original choice. For example, if a user selects test123 and it is taken, NodeBB should suggest 'test123suffix' as an alternative.
Current behaviour:
Expected behaviour:
