_The Instant Cashback product has been retired in favour of Cash Rewards, this release removes endpoints only relevant for that product line._

### Removed

- **Instant Cashback (breaking):** Cashback Calculation - POST `/{version}/offers`
- **Instant Cashback (breaking):** Cashback Expiry - POST `/{version}/offers/{id}/expiry`

### Added

- **Rewards** 
  - Reward Calculation - POST `/2024-02-01/reward-calculations`
- **API** 
  - New calendar based version for the API version
  - Version returned in response headers for all requests to the API
  - API supports Rate limiting
  - Errors returned by the API conform to [RFC 9457 - Problem Details for HTTP APIs](https://www.rfc-editor.org/rfc/rfc9457.html)