Changes to Update a gift card recipient

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

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

removed the request property data/relationships/customer/id

removed the request property data/relationships/customer/type

the request property data/attributes/first_name became nullable

the request property data/attributes/last_name 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 type request property default value gift_card_recipients was removed

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

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