title: MongoDB E11000 duplicate key error with _idi_
body: <p>Trying to create new record at mongoose and getting:</p>
  
  <pre><code>UnhandledPromiseRejectionWarning: MongoError: E11000 duplicate key error collection: admin.inventoryitems index: _id_ dup key: { : ObjectId('5bdf1c4a60ec674ee1a10006') }
  </code></pre>
  
  <p>How I create item:</p>
  
  <pre><code>const createdItem = await InventoryItem.create(item);
  </code></pre>
  
  <p>item doesn't contain an '_id' field</p>