title: Can't retrieve outlook add-in custom properties from graph API
body: <p>I need to save a custom property from my outlook add-in and retrieve the this value from graph Api.</p>
  <p>I followed MS documentation, <a href="https://stackoverflow.com/questions/58166439/expanding-singlevalueextendedproperty-not-working-when-retrieving-event-details">this link</a> and <a href="https://stackoverflow.com/questions/58132732/how-to-check-an-outlook-custom-property-is-available-via-microsoft-graph?answertab=votes#tab-top">this one</a>.</p>
  <p>I store the custom property with office.js methods <code>loadCustomPropertiesAsync</code> and <code>customProps.saveAsync</code></p>
  <p>I have checked the value is correctly stored to custom properties (I can read it from add-in when I come back to event)</p>
  <p>When I try to check the value from graph API, the event is returned without custom props.</p>
  <p>here is the request I use :</p>
  <pre><code>{{endpoint}}/Users/bc2d0290-xxx-4041d2d39b66/Events/AAMkADI1YTJjZTI1LWM4YjUtNxxxTvAAA=?$expand=singleValueExtendedProperties($filter=id eq 'String {00020329-0000-0000-C000-000000000046} Name cecp-myAddInManifestId')
  </code></pre>
  <p>What am I doing wrong ?</p>