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**Description**

In Spark Kubernetes operator we have hard-coded API group and version for spark application k8s object:
https://github.com/apache/airflow/blob/b23a4cd6631ba3346787b285a7bdafd5e71b43b0/airflow/providers/cncf/kubernetes/operators/spark_kubernetes.py#L63-L65
I think it is not good, because we can have situation that some custom or not opensource Spark k8s operators can have different API group and version (like `sparkoperator.mydomain.com` instead of `sparkoperator.k8s.io`). 
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**Use case / motivation**

User have got installed custom or commercial Spark Kubernetes operator and he wants to launch DAG with `SprkKubernetesOperator` from providers. User cannot do that without this implemented feature.

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**Are you willing to submit a PR?**

Yes
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**Related Issues**

No
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tests/providers/cncf/kubernetes/sensors/test_spark_kubernetes.py
"image": "gcr.io/spark-operator/spark:v2.4.4-gcs-prometheus",
        "imagePullPolicy": "Always",
        "mainApplicationFile": "local:///opt/spark/examples/jars/spark-examples_2.11-2.4.4.jar",
        "mainClass": "org.apache.spark.examples.SparkPi",
        "mode": "cluster",
        "monitoring": {
            "exposeDriverMetrics": True,
            "exposeExecutorMetrics": True,
            "prometheus": {
                "jmxExporterJar": "/prometheus/jmx_prometheus_javaagent-0.11.0.jar",
                "port": 8090,
            },
        },
        "restartPolicy": {"type": "Never"},
        "sparkVersion": "2.4.4",
        "type": "Scala",
    },
}
TEST_RUNNING_APPLICATION = {
    "apiVersion": "sparkoperator.k8s.io/v1beta2",
    "kind": "SparkApplication",
    "metadata": {
        "creationTimestamp": "2020-02-26T09:11:25Z",
        "generation": 1,
        "name": "spark-pi",
        "namespace": "default",
        "resourceVersion": "525001",
        "selfLink": "/apis/sparkoperator.k8s.io/v1beta2/namespaces/default/sparkapplications/spark-pi",
        "uid": "95ff1418-eeb5-454c-b59e-9e021aa3a239",
    },