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**Description**

DatabricksRunNowOperator is missing the option to take in key word arguement _jar_params_ , it already can take the other ones notebook_params,python_params,spark_submit_params. https://docs.databricks.com/dev-tools/api/latest/jobs.html#run-now


**Use case / motivation**

Provide parity with the other options

airflow/providers/databricks/operators/databricks.py
},
        }
        notebook_run = DatabricksSubmitRunOperator(task_id='notebook_run', json=json)
    Another way to accomplish the same thing is to use the named parameters
    of the ``DatabricksSubmitRunOperator`` directly. Note that there is exactly
    one named parameter for each top level parameter in the ``runs/submit``
    endpoint. In this method, your code would look like this: ::
        new_cluster = {
          'spark_version': '2.1.0-db3-scala2.11',
          'num_workers': 2
        }
        notebook_task = {
          'notebook_path': '/Users/airflow@example.com/PrepareData',
        }
        notebook_run = DatabricksSubmitRunOperator(
            task_id='notebook_run',
            new_cluster=new_cluster,
            notebook_task=notebook_task)
    In the case where both the json parameter **AND** the named parameters
    are provided, they will be merged together. If there are conflicts during the merge,
    the named parameters will take precedence and override the top level ``json`` keys.
    Currently the named parameters that ``DatabricksSubmitRunOperator`` supports are
        - ``spark_jar_task``
        - ``notebook_task``
        - ``spark_python_task``
        - ``spark_submit_task``
        - ``new_cluster``
        - ``existing_cluster_id``
        - ``libraries``
        - ``run_name``