Assign Promotions to Campaigns with Enhanced OCAPI Data API Endpoint

`/sites/{site_id}/campaigns/{campaign_id}/promotions/{promotion_id}` now allows the `PATCH` method and accepts a body for the `PUT` and `PATCH` methods. This body is identical to the response of the `/sites/{site_id}/promotion_campaign_assignment_search` API, but it now supports a new `required_qualifier` property. With this body, you can set qualifiers and other properties, such as rank, on a promotion assignment when you create it. You can also update these values.