chore: update query

[NowNewNao]

Summary

This PR updates example of halfHourlyReadings query, which was updated on the prod.

• costEstimate added as return value
• productCode is required as one of the query variables

GET_HH_BODY = """
query halfHourlyReadings($accountNumber: String!, $fromDatetime: DateTime, $toDatetime: DateTime, $productCode: String!) {
  account(accountNumber: $accountNumber) {
    properties {
      electricitySupplyPoints {
        halfHourlyReadings(fromDatetime: $fromDatetime, toDatetime: $toDatetime, productCode: $productCode) {
          startAt
          endAt
          version
          value
          costEstimate
        }
      }
    }
  }
}
"""

🤚 Need help

I updated body in octopus.py, but I assume I also need to maintain other place as well such as something like setting def get_product_code(???) -> str: 🙇

[FraserTooth]

If you wanted to use costEstimate you'd have to update this bit with a new line: And also update that dataclass's type with what cost estimate is (probably number?)