Retrieve sync information for all of a user's accounts

Example response

{
  "data": [
    {
      "accountId": "d372d09b-f50a-4114-9c83-687828fa8ac2",
      "lastSuccessfulSync": "2020-07-27T14:33:44+00:00"
    },
    {
      "accountId": "3cc555e4-d954-4eb1-a1df-90df15b132a9",
      "lastSuccessfulSync": null
    }
  ]
}