[Feature] Obtain the Exchange Rate field from somewhere else other than the `receipt` field in Transactions

### Is there an existing feature request for this?

- [X] I have searched the existing issues

### Describe the Feature

Currently, the package obtains the `exchange_rate` field from the Transactions object in a JSON field titled `receipt`. This works to obtain the exchange rate provided within the receipt. However, the receipt for different payment processors is not always the same and also may not be entirely accurate (especially when considering returns).

This FR is to leverage some other method of obtaining the `exchange_rate` field to be used within the downstream transformation logic in this package.

### Describe alternatives you've considered

At the moment we will continue to leverage the `receipt` field in the Transactions table.

Unfortunately, we are unaware if there is another solution. But this FR is intended for the team and community to ideally find an alternative for the package to leverage.

### Are you interested in contributing this feature?

- [ ] Yes.
- [ ] Yes, but I will need assistance and will schedule time during your [office hours](https://calendly.com/fivetran-solutions-team/fivetran-solutions-team-office-hours) for guidance.
- [ ] No.

### Anything else?

_No response_