Members are sometimes given a fee that deviates from the regular
schedule -- e.g. a reduced rate for students -- for a specific period.
Add a per-member "Beitrag" tab where such deviations can be recorded
with a month-granular date range (Ab/Bis), a mandatory reason, and
either a fixed annual amount or a percentage discount off whichever
base rate is in effect at the time.
Data model: ContributionData gets a contribution_overrides list, each
entry validated (month format, Bis >= Ab, non-overlapping ranges per
member, reason required) and CRUD'd through the repository
(record/update/delete/get_contribution_override), consistent with how
donations already work.
Integration: contribution_claims.py now computes each membership-fee
claim's amount month by month instead of a single rate for the whole
billing period, picking up whichever override (if any) covers each
individual month. That handles an override starting or ending mid
period correctly (e.g. a semiannual payer whose discount begins in
March) without changing behavior for members without overrides.
Already-created claims are never recalculated retroactively, matching
how changes to the global contribution rates already behave.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Marcel PeterkauandClaude Sonnet 5