title: Case insensitive search not working with special characters MongoDB
body: <p>In my user authentication I allow users to enter case insensitive <code>email</code>. Recently I saw in the logs that one user can not authenticate himself. Reason is because his <code>email</code> address has <code>+</code> character inside, and for some reason MongoDB case insensitive search can not find email with special characters. It's like the special characters are ignored when performing the regex search.</p>
  <p>I created this testing example: <a href="https://mongoplayground.net/p/sAqSgch9KaN" rel="nofollow noreferrer">Mongo Playground</a></p>
  <p>What is the reason of this behavior and how to solve this?</p>