Currently, the routes `donation/new` and `donation/add` use different parameter names for the amount, some of the names are in German. This has led to confusion and extra code during banner and skin development.
AC:
* amount is provided by `amount` parameter
* English parameters `paymentType` (=`zahlweise`), and `interval` (=`periode`) are used consistently
* All banners are adapted for the new parameters
Note:
New banners must use the new parameter. If the banner markup has different form field names for selected and "input" amount, the banner code must deal with unifying the amount into one parameter.
Related ticket: {T204202}
To be discussed:
* Do we need to accept the legacy German parameters to deal with unconverted banners / oversight on our side
* Log a "notice" when legacy parameters are used, to remind us to convert the parameters?