anchor.diff:  
   union PartnerTypes = ExternalPartner | Partner
   
  +union PaymentMethodUnion = BankAccount | CreditCard | WireTransfer
  +
   enum PhoneNumberErrors {
     INVALID_COUNTRY_CODE
     INVALID_NUMBER
  
positive.code:   # `LOGGED_IN` because we don't know whether or not the authentication is valid
    # (error could be something else).
    authenticationStatus: AuthenticationStatus!
    channel(id: ID!): Channel!
  
    # A list of cities
  
negative.code:   orderHistory: [CommerceOrderEventUnion!]!
    orderUpdateState: String
    paymentMethod: CommercePaymentMethodEnum
    paymentMethodDetails: PaymentMethodUnion
    requestedFulfillment: CommerceRequestedFulfillmentUnion
    seller: CommerceOrderPartyUnion!
    sellerDetails: OrderParty
  