title: Regex for alphanumeric (unicode) with specific length
body: <p>Valid ones should contain at least one number or letter (from 6 to 15 chars long) in any order. e.x.</p>
  
  <pre><code>11111a
  
  111a11
  
  a11111
  </code></pre>
  
  <p>I found similar posts within SO but they seem to be out of order...</p>