Calculate Italian bban checksum code and fix Italian iban generation

[alitaker]

No description provided.

[mdomke]

Hi @alitaker,
I'm not quite sure why the result of the CI pipeline did not get propagated back to this pull-request (I'm gonna look into that), but there are several things that the automatic testing/format-checking did discover (https://travis-ci.org/github/mdomke/schwifty/builds/666876707). Can you please have a look at that?
Thanks for your contribution!

[mdomke]

Please check the development-section of the README. We use black as code-formatter to avoid any discussions about style, because everybody has a different opinion about this…

[alitaker]

Do you think it's ok now?

[mdomke]

@alitaker Even though this is already merged: Are you sure this implementation is actually correct? It looks a little different to this one https://github.com/globalcitizen/php-iban/blob/master/php-iban.php#L1241 Do you maybe have a resource that explains the used algorithm?

[alitaker]

@mdomke I got the information from here:
http://alexandrerodichevski.chiappani.it/doc.php?n=218&lang=it#algo (sorry, it's in Italian).
They are very similar, the only larger difference is that the even digits just use the index for my implementation, while the link you're referring to uses an array of even indices, which are... the indices themselves! (from 1 to 28).
The same for the letters array, which are calculated using the ascii value in the implementation I wrote.
I find the version you linked more elengant, but both will work.

You may test them using the following website for free:
https://it.ibancalculator.com/iban_validieren.html