Changes to Update a free gift promotion

added the new required request property data/relationships/coupon_codes_promotion_rule/data

added the new required request property data/relationships/market/data

added the new required request property data/relationships/order_amount_promotion_rule/data

added the new required request property data/relationships/sku_list/data

added the new required request property data/relationships/sku_list_promotion_rule/data

request property data/type was restricted to a list of enum values

removed the request property data/relationships/coupon_codes_promotion_rule/id

removed the request property data/relationships/coupon_codes_promotion_rule/type

removed the request property data/relationships/market/id

removed the request property data/relationships/market/type

removed the request property data/relationships/order_amount_promotion_rule/id

removed the request property data/relationships/order_amount_promotion_rule/type

removed the request property data/relationships/promotion_rules

removed the request property data/relationships/sku_list/id

removed the request property data/relationships/sku_list/type

removed the request property data/relationships/sku_list_promotion_rule/id

removed the request property data/relationships/sku_list_promotion_rule/type

added the new optional request property data/attributes/_add_tags

added the new optional request property data/attributes/_disable

added the new optional request property data/attributes/_enable

added the new optional request property data/attributes/_remove_tags

added the new optional request property data/attributes/exclusive

added the new optional request property data/attributes/priority

added the new optional request property data/relationships/custom_promotion_rule

added the new optional request property data/relationships/tags

the request property data/attributes/currency_code became nullable

the request property data/attributes/max_quantity became nullable

the request property data/attributes/metadata became nullable

the request property data/attributes/reference became nullable

the request property data/attributes/reference_origin became nullable

the request property data/attributes/total_usage_limit became nullable

the type request property default value free_gift_promotions was removed

added the new free_gift_promotions enum value to the request property data/type

added the media type application/vnd.api+json for the response with the status 200