Pre-calculate the `FixedRateCoupon::amount()`#1759

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ralfkonrad wants to merge 1 commit intolballabio:masterfrom ralfkonrad:very_lazy_fixedratecoupon

+14-20

Commits on Aug 4, 2023

Pre-calculate the FixedRateCoupon::amount(), it isn't mutable
ralfkonrad
committed