Mapping expressions on read and on write

Allows transforming columns as they are being read from the input database and written to the output database.

For example, a column might need a cast to a different type on read and then a cast back to the original type on write. The following configuration might be provided to address that:

tables:
  - table_name_with_schema: "test_schema.test_table"
    mode: "MASKING"
    transformations:
      - columns: ["my_binary_column"]
        mapping:
          read: "cast(? as char)"
          write: "cast(? as binary)"

The my_binary_column will be cast to char type on read and the result of transformation will be cast back to binary type on write.