rpc CommitTransaction(CommitTransactionRequest) returns (CommitTransactionResponse);

    rpc NewTransaction(Transaction) returns (TransactionReturn);
    rpc LastTransaction() returns (TransactionReturn);

    map<string, string> identifiers; // key is system name and value is identifier in that system

    Invalidate invalidate = 1;

    optional Invalidate invalidate = 1;

    Invalidate invalidate = 1;

    optional Invalidate invalidate = 1;

    Invalidate invalidate = 1;

    optional Invalidate invalidate = 1;
}
enum PaymentType {
    PAY_CASH = 0;
    PAY_CARD = 1;
    PAY_CRYPTO = 3;
    PAY_PAYPAL = 4;
    PAY_VIPS = 5;
}
message Payment {
    PaymentType type = 0;
    Money amount = 1;
    Timestamp ts = 2;
    optional uint64 customer = 3; // tid of the customer payed
}
message Customer {
    string name = 0;
    string address = 1;
    map<string, string> identifiers = 2; // identifers of that customer in different systems
    optional string comment = 3;
    repeated string tags;

    }
}
message TransactionReturn {
    oneof return_value {
        Transaction tr = 0;
        Error err = 1;