R4 APIs (Millennium)

I need your help on how to process heart rate to post it to Cerner as observation

Also, please provide the list of Cerner supported “LOINC Code” for below list
1. Respiration Rate
2. Pulse Oximetry
3. Heart Rate
4. BMI
5. HDL
6. Triglycerides
7. Blood Sugar / Random Blood Glucose
8. Alcohol

I am posting below request, but getting the error “StatusCode: 422, ReasonPhrase: 'Unprocessable Entity'”

Error Message:

{
    "resourceType": "OperationOutcome",
    "issue": [
        {
            "severity": "error",
            "code": "invalid",
            "details": {
                "text": "Unprocessable entity"
            }
        }
    ]
}

Payload

{
    "resourceType": "Observation",
    "status": "final",
    "category": [
        {
            "coding": [
                {
                    "system": "http://terminology.hl7.org/CodeSystem/observation-category",
                    "code": "vital-signs",
                    "display": "Vital Signs"
                }
            ],
            "text": "Vital Signs"
        }
    ],
    "code": {
        "coding": [
            {
                "system": "http://loinc.org",
                "code": "8889-8",
                "display": "Heart rate by Pulse oximetry"
            }
        ],
        "text": "Heart rate"
    },
    "subject": {
        "reference": "Patient/12724067"
    },
    "encounter": {
        "reference": "Encounter/97959035"
    },
    "effectiveDateTime": "2023-06-08T02:44:18.757.000z",
    "issued": "2023-06-08T02:44:18.757.000z",
    "performer": [
        {
            "reference": "Practitioner/12732062",
            "display": "legal authenticator"
        }
    ],
    "valueQuantity": {
        "value": 78,
        "unit": "bpm",
        "system": "http://unitsofmeasure.org",
        "code": "/min"
    },
    "note": [
        {
            "authorReference": {
                "reference": "Practitioner/12732062"
            },
            "time": "2023-06-08T02:44:18.000z",
            "text": "No additional details required"
        }
    ]
}