title: Spaces in YAML keys
body: <p>Is there a correct way to use spaces in YAML keys? Like</p>
  
  <pre><code>a test: "hello world!" 
  </code></pre>
  
  <p>or</p>
  
  <pre><code>"a test": "hello world!"
  </code></pre>
  
  <p>or is it just a bad idea and one should use</p>
  
  <pre><code>a_test: "hello world!"
  </code></pre>
  
  <p>All of them seem valid in a yaml-Linter, but I didn't find any examples online using spaces in a key.</p>