Support POST /v1/items/check-integrity

`POST /v1/items/check-integrity`
```json
{
    "integrityPayloads": [
        {
            "uuid": "a19606e7-5838-4c7f-9641-93ffdcacf3c2"
        }
    ]
}
```

https://github.com/standardnotes/standalone does not support yet this feature.