#21 Filename of download german banks file does not honor valid range

[Ralf Habacker]

The bank details downloaded from https://www.bundesbank.de/de/aufgaben/unbarer-zahlungsverkehr/serviceangebot/bankleitzahlen/download-bankleitzahlen-602592 are each valid for 3 months, from 4.12.y, 4.3.y+1, 4.6.y+1, 4.9.y+1 to 3.6.y, 3.9.y, 3.12.y, 3.3.y+1 (in German date format, y = year)

The file name of the downloaded file does not currently reflect these date ranges as it is saved under the current date. The file name should correspond to the beginning of one of the listed ranges to avoid redundant updates that differ only in the file name.