QMUX key pcode attribute

[ar]

In addition to the 'mti' attribute, there are some use cases where the key also depends on the processing code.

A nice enhacement, based on @galihlasahido suggestion would be to have a companion optional 'pcode' attribute, something like this:

<key mti="0200" pcode="381000">7 11</key>
<key mti="0200" pcode="XXXXXX">7 11 41</key>
...

[ar]

Background conversation and reference code: https://www.linkedin.com/pulse/jpos-multiple-key-mux-setting-application-galih-lasahido-pyudc/