Instance is a payment service PayPal, which supply only parameters (yet not support xml or json ).
Our callable service receive data (which only few is impotant for us).
PayPal require resend all recieve paramters to verify data. If only one of this parameters is missing or blank, then PayPal send response that request is INVALID, that's mean that someone try swindle. This isn't always true, because maybe we resend not completed request. But we have to reject incoming payments.
Parameters from PayPal depend on type of payment e.g. web payment, credit card etc. In future additonal parameters may be added by PayPal , and this is problem because we must rebuild callable service and we are not sure that all trigger are implemented.
On the other hand this is "Sisyphean job" because we must map all parameter name as key and concatenate to one request with value. And PayPal require order paramters by FIFO. All of this causes that this is hard to maintain and develop.
Regards Paweł Goc
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