title: gtag not sending custom dimensions for events
body: <p>I'm having trouble using gtag to send to custom dimensions. I'm currently following <a href="https://developers.google.com/analytics/devguides/collection/gtagjs/custom-dims-mets" rel="noreferrer">their gtag documentation</a>. </p>
  
  <p>Screenshot of the custom dimensions created for my google analytics property
  <a href="https://i.stack.imgur.com/k2Oq4.png" rel="noreferrer"><img src="https://i.stack.imgur.com/k2Oq4.png" alt="enter image description here"></a></p>
  
  <p>Right now I currently initialize my gtag in the head with the following code:</p>
  
  <pre><code>%script{:async =&gt; "", :src =&gt; "https://www.googletagmanager.com/gtag/js?id=#{APP_CONFIG[:ga_tracking_code]}"}
  :javascript
    window.dataLayer = window.dataLayer || [];
    function gtag(){dataLayer.push(arguments);}
    gtag('js', new Date());
    gtag('config', '#{APP_CONFIG[:ga_tracking_code]}', {
     'custom_map': {
                     'dimension1': 'user_type'
                     'dimension2': 'organization_id'
                   }
    });
  </code></pre>
  
  <p>Events are currently logged like this</p>
  
  <pre><code>gtag('event', 'test_event', {
                               'event_category': 'test_category', 
                               'organization_id': 'test_org',
                               'user_type': 'test_user_type'
                              });
  </code></pre>
  
  <p>Looking forward to responses as I have not made progress figuring this out for the past two days.</p>