title: How to get Google Sheets sidebar input to server
body: <p>I am creating a dialog to show and edit document properties in a sidebar of Google Spreadsheets.</p>
  
  <p>I managed to show the property values in the sidebar and even create text input fields to interact with via the sidebar. But finally I'm not able to get the values back into the server-side script using a serverHandler.</p>
  
  <p>How are interactive dialogs with a sidebar are supported in Google Sheets?</p>