Allow a list of SQL statements in GenericTransfer

[dabla]

Allow a list of SQL statements to be passed to the GenericTransfer just like the SQLExecuteQueryOperator to avoid the need to use partial/expand which is way more expensive than looping over the SQL-statements within the operator.

The use-case is inspired from this medium article where there it was still using partial/expand.

An example:

load_retrieved_files_to_db = GenericTransfer(
    task_id="load_retrieved_files_to_db",
    source_conn_id="duckdb_duckdb_memory",
    destination_conn_id=MSSQL_CONN_ID,
    destination_table="BRONZE.log_files",
    sql=retrieved_files.output.map(
       lambda file: f"""
       SELECT *
       FROM read_csv(
           '{file}',
           delim = ';',
           header = false,
           columns = {{
               'event_id': 'INTEGER',
               'event_time': 'TIMESTAMP',
               'event': 'VARCHAR',
               'result': 'VARCHAR',
               'info': 'VARCHAR',
               'user_id': 'VARCHAR',
               'origin': 'VARCHAR',
               'destination': 'VARCHAR',
               'session_id': 'INTEGER'
           }}
       );
    """
    ),
    insert_args={
        "target_fields": [
            "event_id",
            "event_time",
            "event",
            "result",
            "info",
            "user_id",
            "origin",
            "destination",
            "session_id",
        ],
        "commit_every": 5000,
        "executemany": True,
        "fast_executemany": True,
    },
)

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