Support CSV column renaming without having to use custom scripts

[adlersantos]

Description

CSV column name remapping is a very common use case for data transforms.

To prevent contributors from having to keep writing a custom script to rename CSV columns, we can have a column name mapping feature built right into the YAML config file.

We can represent it as an operator such as:

dag:
  tasks:
    - operator: "RenameCSVHeadersOperator"
      source_csv: "gs://bucket/path/to/file.csv"
      mappings:
        - old_header: "DATE"
          new_header: "date"
        - old_header: "FACILITY_NAME"
          new_header: "facility_name"

Checklist

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