Requests with large IDs end up with an Internal Server Error

Looks like Duffy has some issues when it comes to handling large IDs (for tenants/nodes/sessions/etc.):

```
$ curl -X 'GET' "https://duffy.ci.centos.org/api/v1/nodes/123123133333311111111111111111111111111111111111111111" -H 'accept: application/json' -H 'Authorization: Basic xxxxx'
Internal Server Error
```