temp.json

[
    {
        "op": "remove",
        "path": "/spec/template/spec/containers/0/env"
    },
    {
        "op": "add",
        "path": "/spec/template/spec/containers/0/env",
        "value": [
            {
                "name": "DB_User",
                "valueFrom": {
                    "secretKeyRef": {
                        "key": "DB_User",
                        "name": "prod-db"
                    }
                }
            },
            {
                "name": "DB_Host",
                "valueFrom": {
                    "secretKeyRef": {
                        "key": "DB_Host",
                        "name": "prod-db"
                    }
                }
            },
            {
                "name": "DB_Password",
                "valueFrom": {
                    "secretKeyRef": {
                        "key": "DB_Password",
                        "name": "prod-db"
                    }
                }
            }
        ]
    ]