Gets default store view code correctly

[netorodrigues]

Questions	Answers
Issue	https://mundipagg.atlassian.net/browse/PAOP-120
What?	Gets the correct store code before building installments url.
Why?	To fix a bug when creating a order from admin if the user changes the code of the default store.
How?	Getting the store's code saved in magento side instead of letting it hardcoded.

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