Changes to Create a customer

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

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

removed the request property data/relationships/customer_group/id

removed the request property data/relationships/customer_group/type

added the new optional request property data/attributes/profile_id

added the new optional request property data/attributes/shopper_reference

added the new optional request property data/attributes/tax_exemption_code

added the new optional request property data/relationships/tags

the type request property default value customers was removed

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

added the media type application/vnd.api+json for the response with the status 201