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Membership Contributions - Overview

Project: Mila - Membership Management System
Feature: Membership Contribution Management
Version: 1.0
Last Updated: 2025-11-27
Status: Concept - Ready for Review

Purpose

This document provides a comprehensive overview of the Membership Contributions system. It covers business logic, data model, UI/UX design, and technical architecture in a concise, bullet-point format.

For detailed implementation: See contributions-implementation-plan.md (created after concept iterations)

Core Principle
Terminology
Data Model
Business Logic
UI/UX Design
Edge Cases
Technical Integration
Implementation Scope

Core Principle

Maximum Simplicity:

Minimal complexity
Clear data model without redundancies
Intuitive operation
Calendar period-based (Month/Quarter/Half-Year/Year)

Terminology

German ↔ English

Core Entities:

Beitragsart ↔ Contribution Type / Membership Fee Type
Beitragsintervall ↔ Contribution Period
Mitgliedsbeitrag ↔ Membership Fee / Contribution

Status:

bezahlt ↔ paid
unbezahlt ↔ unpaid
ausgesetzt ↔ suspended / waived

Intervals:

monatlich ↔ monthly
quartalsweise ↔ quarterly
halbjährlich ↔ half-yearly / semi-annually
jährlich ↔ yearly / annually

UI Elements:

"Letztes Intervall" ↔ "Last Period" (e.g., 2023 when in 2024)
"Aktuelles Intervall" ↔ "Current Period" (e.g., 2024)
"Als bezahlt markieren" ↔ "Mark as paid"
"Aussetzen" ↔ "Suspend" / "Waive"

Data Model

Contribution Type (ContributionType)

- id (UUID)
- name (String) - e.g., "Regular", "Reduced", "Student"
- amount (Decimal) - Contribution amount in Euro
- interval (Enum) - :monthly, :quarterly, :half_yearly, :yearly
- description (Text, optional)
- timestamps

Important:

interval is IMMUTABLE after creation!
Admin can only change name, amount, description
On change: Future unpaid periods regenerated with new amount

Contribution Period (ContributionPeriod)

- id (UUID)
- member_id (FK → members.id)
- contribution_type_id (FK → contribution_types.id)
- period_start (Date) - Calendar period start (01.01., 01.04., 01.07., 01.10., etc.)
- status (Enum) - :unpaid (default), :paid, :suspended
- amount (Decimal) - Amount at generation time (history when type changes)
- notes (Text, optional) - Admin notes
- timestamps

Important:

NO period_end - calculated from period_start + interval
NO interval_type - read from contribution_type.interval
Avoids redundancy and inconsistencies!

Calendar Period Logic:

Monthly: 01.01. - 31.01., 01.02. - 28./29.02., etc.
Quarterly: 01.01. - 31.03., 01.04. - 30.06., 01.07. - 30.09., 01.10. - 31.12.
Half-yearly: 01.01. - 30.06., 01.07. - 31.12.
Yearly: 01.01. - 31.12.

Member (Extensions)

- contribution_type_id (FK → contribution_types.id, NOT NULL, default from settings)
- contribution_start_date (Date, nullable) - When to start generating contributions
- left_at (Date, nullable) - Exit date (existing)

Logic for contribution_start_date:

Auto-set based on global setting include_joining_period
If include_joining_period = true: First day of joining month/quarter/year
If include_joining_period = false: First day of NEXT period after joining
Can be manually overridden by admin

NO include_joining_period field on Member - unnecessary due to contribution_start_date!

Global Settings

key: "contributions.include_joining_period" 
value: Boolean (Default: true)

key: "contributions.default_contribution_type_id"
value: UUID (Required) - Default contribution type for new members

Meaning include_joining_period:

true: Joining period is included (member pays from joining period)
false: Only from next full period after joining

Meaning default_contribution_type_id:

Every new member automatically gets this contribution type
Must be configured in admin settings
Prevents: Members without contribution type

Business Logic

Period Generation

Triggers:

Member gets contribution type assigned (also during member creation)
New period begins (Cron job daily/weekly)
Admin requests manual regeneration

Algorithm:

Get member.contribution_start_date and member.contribution_type
Calculate first period based on contribution_start_date
Generate all periods from start to today (or left_at if present)
Skip existing periods
Set amount to current contribution_type.amount

Example (Yearly):

Joining date: 15.03.2023
include_joining_period: true
→ contribution_start_date: 01.01.2023

Generated periods:
- 01.01.2023 - 31.12.2023 (joining period)
- 01.01.2024 - 31.12.2024
- 01.01.2025 - 31.12.2025 (current year)

Example (Quarterly):

Joining date: 15.03.2023
include_joining_period: false
→ contribution_start_date: 01.04.2023

Generated periods:
- 01.04.2023 - 30.06.2023 (first full quarter)
- 01.07.2023 - 30.09.2023
- 01.10.2023 - 31.12.2023
- 01.01.2024 - 31.03.2024
- ...

Status Transitions

unpaid → paid
unpaid → suspended
paid → unpaid
suspended → paid
suspended → unpaid

Permissions:

Admin + Treasurer (Kassenwart) can change status
Uses existing permission system

Contribution Type Change

MVP - Same Interval Only:

Member can only choose contribution type with same interval
Example: From "Regular (yearly)" to "Reduced (yearly)" ✓
Example: From "Regular (yearly)" to "Reduced (monthly)" ✗

Logic on Change:

Check: New contribution type has same interval
If yes: Set member.contribution_type_id
Future unpaid periods: Delete and regenerate with new amount
Paid/suspended periods: Remain unchanged (historical amount)

Future - Different Intervals:

Enable interval switching (e.g., yearly → monthly)
More complex logic for period overlaps
Needs additional validation

Member Exit

Logic:

Periods only generated until member.left_at
Existing periods remain visible
Unpaid exit period can be marked as "suspended"

Example:

Exit: 15.08.2024
Yearly period: 01.01.2024 - 31.12.2024

→ Period 2024 is shown (Status: unpaid)
→ Admin can set to "suspended"
→ No periods for 2025+ generated

UI/UX Design

Member List View

New Column: "Contribution Status"

Default Display (Last Period):

Shows status of last completed period
Example in 2024: Shows contribution for 2023
Color coding:
- Green: paid ✓
- Red: unpaid ✗
- Gray: suspended ⊘

Optional: Show Current Period

Toggle: "Show current period" (2024)
Admin decides what to display

Filters:

"Unpaid contributions in last period"
"Unpaid contributions in current period"

Member Detail View

Section: "Contributions"

Contribution Type Assignment:

┌─────────────────────────────────────┐
│ Contribution Type: [Dropdown]       │
│ ⚠ Only types with same interval    │
│   can be selected                   │
└─────────────────────────────────────┘

Period Table:

┌───────────────┬──────────┬────────┬──────────┬─────────┐
│ Period        │ Interval │ Amount │ Status   │ Action  │
├───────────────┼──────────┼────────┼──────────┼─────────┤
│ 01.01.2023-   │ Yearly   │ 50 €   │ ☑ Paid   │         │
│ 31.12.2023    │          │        │          │         │
├───────────────┼──────────┼────────┼──────────┼─────────┤
│ 01.01.2024-   │ Yearly   │ 60 €   │ ☐ Open   │ [Mark   │
│ 31.12.2024    │          │        │          │ as paid]│
├───────────────┼──────────┼────────┼──────────┼─────────┤
│ 01.01.2025-   │ Yearly   │ 60 €   │ ☐ Open   │ [Mark   │
│ 31.12.2025    │          │        │          │ as paid]│
└───────────────┴──────────┴────────┴──────────┴─────────┘

Legend: ☑ = paid | ☐ = unpaid | ⊘ = suspended

Quick Marking:

Checkbox in each row for fast marking
Button: "Mark selected as paid"
Bulk action for multiple periods

Admin: Contribution Types Management

List:

┌────────────┬──────────┬──────────┬────────────┬─────────┐
│ Name       │ Amount   │ Interval │ Members    │ Actions │
├────────────┼──────────┼──────────┼────────────┼─────────┤
│ Regular    │ 60 €     │ Yearly   │ 45         │ [Edit]  │
│ Reduced    │ 30 €     │ Yearly   │ 12         │ [Edit]  │
│ Student    │ 20 €     │ Monthly  │ 8          │ [Edit]  │
└────────────┴──────────┴──────────┴────────────┴─────────┘

Edit:

Name: ✓ editable
Amount: ✓ editable
Description: ✓ editable
Interval: ✗ NOT editable (grayed out)

Warning on Amount Change:

⚠ Change amount to 65 €?
  
Impact:
- 45 members affected
- Future unpaid periods will be generated with 65 €
- Already paid periods remain with old amount

[Cancel] [Confirm]

Admin: Settings

Contribution Configuration:

Default Contribution Type: [Dropdown: Contribution Types]

Selected: "Regular (60 €, Yearly)"

This contribution type is automatically assigned to all new members.
Can be changed individually per member.

---

☐ Include joining period

When active:
Members pay from the period of their joining.

Example (Yearly):
Joining: 15.03.2023
→ Pays from 2023

When inactive:
Members pay from the next full period.

Example (Yearly):
Joining: 15.03.2023
→ Pays from 2024

Edge Cases

1. Contribution Type Change with Different Interval

MVP: Blocked (only same interval allowed)

UI:

Error: Interval change not possible

Current contribution type: "Regular (Yearly)"
Selected contribution type: "Student (Monthly)"

Changing the interval is currently not possible.
Please select a contribution type with interval "Yearly".

[OK]

Future:

Allow interval switching
Calculate overlaps
Generate new periods without duplicates

2. Exit with Unpaid Contributions

Scenario:

Member exits: 15.08.2024
Yearly period 2024: unpaid

UI Notice on Exit:

⚠ Unpaid contributions present

This member has 1 unpaid period(s):
- 2024: 60 € (unpaid)

Do you want to continue?

[ ] Mark contribution as "suspended"
[Cancel] [Confirm Exit]

3. Multiple Unpaid Periods

Scenario: Member hasn't paid for 2 years

Display:

┌───────────────┬──────────┬────────┬──────────┬─────────┐
│ 2023          │ Yearly   │ 50 €   │ ☐ Open   │ [✓]     │
│ 2024          │ Yearly   │ 60 €   │ ☐ Open   │ [✓]     │
│ 2025          │ Yearly   │ 60 €   │ ☐ Open   │ [ ]     │
└───────────────┴──────────┴────────┴──────────┴─────────┘

[Mark selected as paid] (2 selected)

4. Amount Changes