title: Unsubscribing from Observable in a non-Component/Directive class
body: <p>I've read tons of posts on unsubscribing from <code>Observable</code>s in Angular and all of them mention the need to do so in components/directives only.</p>
  
  <p>So my question is:  </p>
  
  <p>Do we need to unsubscribe from <code>Observable</code>s in a non-component/directive class e.g. in a service or basically any other class that contains subscriptions to <code>Observable</code>s?</p>