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Fixes missing assignment of response code
Use wrapper for http requests instead of using HttpRequest directly.

* Add AuthenticationException which is thrown on unsuccessful login
* Add headers to BankRequest
* Move DefaultBankResponse to test package and renamed it to MockedBankResponse
Move username and password properties to parent class
Use wrapper for http requests instead of using HttpRequest directly.

* Add AuthenticationException which is thrown on unsuccessful login
* Add headers to BankRequest
* Move DefaultBankResponse to test package and renamed it to MockedBankResponse
Use wrapper for HttpRequests