The provider is indirectly identified by *dataCenterId* inside

    POST /api/enstratus/2011-12-15/infrastructure/Server

```json
{"launch":
[
{
"terminateAfter":"2011-12-15T19:31:41.502-0600",
"product":{"productId":""},
"firewalls":[{"firewallId":3064},{"firewallId":3263}],
"scripts":[{"sharedScriptCode":"1-1"},{"sharedScriptCode":"500-1"}],
"cmAccount":{"cmAccountId":1},
"machineImage":{"machineImageId":70000},
"description":"Created by the enStratus unit tests.",
"name":"Unit Test 1323997299",
"label":"red",
"dataCenter":{"dataCenterId":942}
}
]
```

at the moment it is extracted from the MachineImage obj, but probably it should be the other way round: given a datacenterId, retrieve all the machineImage available and pick the most appropriate one from this set.