[backend] Tornjak Clusters API cleanup

[maia-iyer]

The code currently defines cluster using this type:

{
  "cluster": {
    "name": "clusterName",
    "platformType": "Docker",
    "agentsList": [
      "agent1"
    ],
    "domainName": "example.org",
    "editedName": "",
    "creationTime": "Feb 08 2023 21:02:10",
    "managedBy": ""
  }
}

The 'editedName' is improper and throws weird, unexpected errors at times. Instead, it would be better to have some UID for a cluster, which can be passed in.

This also eventually affects the frontend call to this API.

[jxia20]

RCOS - Jimi Xia

[DashLHall]

Dashiell, RCOS group

[ArnavPawar]

RCOS - Arnav Pawar