[Discussion] Conversion amount for use in `dbt_apple_search_ads` reports.

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

- [X] I have searched the existing issues

### Describe the Feature

The Apple App Store source package currently does not include the `sales_purchasable_item_source_type_report` table. Adding this table could be beneficial for the [`dbt_apple_search_ads`](https://github.com/fivetran/dbt_apple_search_ads) package, as Apple Search Ads does not provide a direct `conversion_value` field. The `sales_purchasable_item_source_type_report` table, available in the Apple App Store connector, tracks app and in-app purchases. By filtering the `sales` field where `source_type = 'App Store Search'`, users can obtain insights into purchases that originated from App Store search activity. This may serve as a useful alternative for conversion value. More details can be found in [Apple's Sales and Trends metrics and dimensions documentation](https://developer.apple.com/help/app-store-connect/reference/sales-and-trends-metrics-and-dimensions/).

Is this a feature you are interested in are would like to contribute to? Let us know in the comments!

### How would you implement this feature?

Add `sales_purchasable_item_source_type_report` to the source. In downstream uses, it's not clear how to join this data, however.

### Describe alternatives you've considered

_No response_

### Are you interested in contributing this feature?

- [X] Yes.
- [ ] Yes, but I will need assistance.
- [ ] No.

### Anything else?

_No response_

Start by reviewing the existing Apple App Store source tables and Apple's Sales and Trends metrics and dimensions documentation. Add sales_purchasable_item_source_type_report to the source, and confirm how its sales field filtered by source_type = 'App Store Search' should be joined for downstream use; the join remains unresolved in the issue.

Written by the indexing model from the issue text.