expressCart/config/payment/schema/instore.json

{
    "properties": {
        "orderStatus": {
            "type": "string",
            "enum": ["Completed", "Paid", "Pending"]
        },
        "buttonText": {
            "type": "string"
        },
        "resultMessage": {
            "type": "string"
        }
    },
    "required": [
        "orderStatus",
        "buttonText",
        "resultMessage"
    ],
    "additionalProperties": false
}