title: POSTing a new item to a SharePoint list using the MS Graph API with a People field
body: <p>I have set up a React web app consuming data using Microsoft Graph from SharePoint Online which is working well. I can read and write to SP Lists, but I am unable to find any documentation regarding how to structure the data to write into a 'People/Group' field.</p>
  
  <p>Querying a list with these fields yields <code>"ManagerLookupId": "12"</code>, where <code>Manager</code> is the People Picker field name. I can resolve the <code>"12"</code> by using the expand query string. I can't figure out how to write to it using either the <code>/v1.0</code> or <code>/beta</code> endpoints from Microsoft Graph</p>
  
  <p>Posting this object to the relevant endpoint works (for Single Line Text, Choice, etc).</p>
  
  <pre><code>{
    "fields": {
      "Title": "a",
      "Category": "b",
      "Description": "c"
    }
  }
  </code></pre>
  
  <p>But if I were to add in the People picker field, I don't know how to structure that data. I have tried email address and GUID, both of which didn't work. Looking at how SP does it natively, it appears to submit this value on submission for the people picker field (have replaced real values) - </p>
  
  <pre><code>{
    "Key": "i:0#.f|membership|EMAIL",
    "DisplayText": "NAME",
    "IsResolved": true,
    "Description": "EMAIL",
    "EntityType": "User",
    "EntityData": {
      "IsAltSecIdPresent": "False",
      "Title": "POSITION",
      "Email": "EMAIL",
      "MobilePhone": "",
      "ObjectId": "GUID",
      "Department": ""
    },
    "MultipleMatches": [],
    "ProviderName": "Tenant",
    "ProviderDisplayName": "Tenant"
  }
  </code></pre>
  
  <p>Replicating this also fails to update the People field in the list.</p>
  
  <p>I wasn't able to find any documentation on the MS Graph API site or similar previous questions on their Github, so any help would be really appreciated!</p>