title: Retrofit2 Passing List as Url parameter
body: <p>I am trying to make a GET request with a string list.</p>
  
  <p>Retrofit representing list like this;</p>
  
  <pre><code>/endpoint?GTIN=111&amp;GTIN=222
  </code></pre>
  
  <p>But server (Springboot) only giving results for the last one.</p>
  
  <p>It works with this</p>
  
  <pre><code>/endpoint?GTIN=111,222
  </code></pre>
  
  <p>Is there a way of doing the latter in retrofit?</p>