ROX-21118: change expired_at via API

[parametalol]

$ curl -H "Authorization: Bearer $STATIC_TOKEN_ADMIN" \
"http://localhost:8000/api/rhacs/v1/admin/centrals/cl75fu8bs0bd6k334h0g/expired-at" \
-d "timestamp=2024-01-02T13:45:56Z" \
-d "reason=test" -X PATCH

Logs:

W1127 09:29:41.074361      13 admin_dinosaur.go:258] Setting expired_at to "2024-01-02T13:45:56Z" for central "cl75fu8bs0bd6k334h0g": test
I1127 09:29:41.076758      13 framework.go:51] user='rhacs-ms-test@redhat.com' action='admin-expired-at' src_ip='127.0.0.1:60156' session='20873d12-aae8-4d3b-9c14-44a5a253c367' tx_id='631' opid='cli631dfh90d6k12pjdg' operation ended successfully

expired_at field in GET centrals:

$ curl -H "Authorization: Bearer $STATIC_TOKEN_ADMIN" "http://localhost:8000/api/rhacs/v1/admin/centrals"

{
  "kind": "CentralList",
  "page": 1,
  "size": 1,
  "total": 1,
  "items": [
    {
      "id": "cl75fu8bs0bd6k334h0g",
      "kind": "CentralRequest",
      "href": "/api/rhacs/v1/centrals/cl75fu8bs0bd6k334h0g",
      "status": "ready",
      "cloud_provider": "aws",
      "multi_az": true,
      "region": "us-east-1",
      "owner": "acscs-trial-expiration-test-prod",
      "name": "test-central-1",
      "host": "acs-cl75fu8bs0bd6k334h0g.cluster.local",
      "created_at": "2023-11-10T16:19:06.767675Z",
      "updated_at": "2023-11-27T14:22:24.692756Z",
      "expired_at": "2024-01-02T13:45:56Z",
      "failed_reason": "Creation time went over the timeout. Interrupting central initialization.",
      "instance_type": "standard"
    }
  ]
}

[stehessel]

LGTM, modulo the log which is wrong if ts == "".

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[openshift-ci]

New changes are detected. LGTM label has been removed.