FinTS: Robustness

[mtotschnig]

• Passwort cannot be changed: Currently the password provided by the user is both used for encrypting the data file and for communication with the FinTS server, which makes the connection unusable once the banking credentials need to be changed, because the data file cannot be decrypted with the new password.
• Multiple challenges per session fail: If during a session, the bank requests more than one TAN, currently the communication will fail. because our implementation returns the response to the first challenge to all subsequent challenges.
• Support for Commerzbank: Commerzbank fails because of format of account parameter
• Support for Sparkasse: broken since version 3.8.6 (https://github.com/hbci4j/hbci4java/issues/92)

[mtotschnig]

Howto migrate existing banks to the new mechanism: The context menu for the bank has an entry labelled "v1 -> v2" It opens a dialog that allows to provide the original PIN needed for decrypting the passport file: