Changes to Update a customer group

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

added the new optional request property data/attributes/code

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 customer_groups was removed

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

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