title: Remove extra spaces from entire sentence
body: <p>I have below variable</p>
  
  <pre><code>sen &lt;- "I have a    sentence  "
  </code></pre>
  
  <p>I just want to remove spaces from above sentence (all of spaces, beginning end &amp; middle), I know how to use <code>str_trim(sen)</code>, but that only removes beginning &amp; end spaces.I want to get rid of middle as well</p>
  
  <p>Required Output "I have a sentence"</p>