feat: add bieannial and triannial billing frequency

[HenningWendtland]

Addition of biennial and triennial billing (every 2 and 3 years).
This was easily possible for the period_type == "start date" but not for "calendar months" type, so just implemented for the first type.
To improve the UI the correct types are displayed dynamically

Reference: AIT-46

[greptile-apps]

Confidence Score: 5/5

Safe to merge. The biennial/triennial date arithmetic is correct, all four period_type × billing_time combinations are covered, and the new tests verify the boundary cases including the cross-year block alignment.

The block-anchor formula start_year + (Δyears // years_span) * years_span correctly handles forward and backward navigation through biennial and triennial calendar windows. The validate() hook reliably gates the multi-year + CalendarMonths combination at save time, and create_current_invoice catches the matching ValueError at run time. No new failure modes were introduced relative to the existing handling of Yearly/Halfyearly frequencies.

No files require special attention.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A([get_from_and_to_date]) --> B{period_type?}
    B -- StartDate --> C{billing_time?}
    B -- CalendarMonths --> D{billing_time?}

    C -- AtBeginning --> E[get_date_period\neval_date, freq, start_date]
    C -- AfterEnd --> F[get_date_period\ncurrent_start - 1d, freq, start_date]

    D -- AtBeginning --> G[get_calendar_period\neval_date, freq, start_year]
    D -- AfterEnd --> H[get_calendar_period\ncurrent_start - 1d, freq, start_year]

    G --> I{freq in\nMULTI_YEAR?}
    H --> I

    I -- Yes\nBiennial/Triennial --> J[block_start_year =\nstart_year + floor_div x years_span\nfrom_date = date block_start_year 1 1]
    I -- No\nMonthly/Quarterly/\nHalfyearly/Yearly --> K[from_date via\nINVOICE_MONTH_MAP]

    J --> L[to_date = from_date +\nrelativedelta months=freq.value - 1 day]
    K --> L
    E --> M([return from_date, to_date])
    F --> M
    L --> M

Loading

%%{init: {'theme': 'base', 'themeVariables': {"darkMode": true, "background": "#0d1117", "primaryColor": "#21262d", "primaryTextColor": "#e6edf3", "primaryBorderColor": "#8b949e", "lineColor": "#8b949e", "textColor": "#e6edf3", "edgeLabelBackground": "#161b22", "actorBkg": "#21262d", "actorBorder": "#8b949e", "actorTextColor": "#e6edf3", "actorLineColor": "#8b949e", "signalColor": "#8b949e", "signalTextColor": "#e6edf3", "noteBkgColor": "#373320", "noteBorderColor": "#d4a72c", "noteTextColor": "#f0e6c0", "labelBoxBkgColor": "#21262d", "labelBoxBorderColor": "#8b949e", "labelTextColor": "#e6edf3", "loopTextColor": "#e6edf3", "activationBkgColor": "#30363d", "activationBorderColor": "#8b949e"}}}%%
flowchart TD
    A([get_from_and_to_date]) --> B{period_type?}
    B -- StartDate --> C{billing_time?}
    B -- CalendarMonths --> D{billing_time?}

    C -- AtBeginning --> E[get_date_period\neval_date, freq, start_date]
    C -- AfterEnd --> F[get_date_period\ncurrent_start - 1d, freq, start_date]

    D -- AtBeginning --> G[get_calendar_period\neval_date, freq, start_year]
    D -- AfterEnd --> H[get_calendar_period\ncurrent_start - 1d, freq, start_year]

    G --> I{freq in\nMULTI_YEAR?}
    H --> I

    I -- Yes\nBiennial/Triennial --> J[block_start_year =\nstart_year + floor_div x years_span\nfrom_date = date block_start_year 1 1]
    I -- No\nMonthly/Quarterly/\nHalfyearly/Yearly --> K[from_date via\nINVOICE_MONTH_MAP]

    J --> L[to_date = from_date +\nrelativedelta months=freq.value - 1 day]
    K --> L
    E --> M([return from_date, to_date])
    F --> M
    L --> M

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_{Reviews (4): Last reviewed commit: "fix: pass only start_year and replace fr..." | Re-trigger Greptile}

[HenningWendtland]

@greptileai

[HenningWendtland]

@greptileai

[barredterra]

One last nitpick

[barredterra]

@greptileai

[barredterra]

@Mergifyio backport version-15

[mergify]

backport version-15

✅ Backports have been created

Details

• #9 feat: add bieannial and triannial billing frequency (backport #8) has been created for branch version-15 but encountered conflicts

Cherry-pick of 57f176b has failed:

On branch mergify/bp/version-15/pr-8
Your branch is up to date with 'origin/version-15'.

You are currently cherry-picking commit 57f176b.
  (fix conflicts and run "git cherry-pick --continue")
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Changes to be committed:
	modified:   README.md
	modified:   simple_subscription/locale/de.po
	modified:   simple_subscription/locale/main.pot
	modified:   simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.json

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   simple_subscription/simple_subscription/doctype/simple_subscription/simple_subscription.py
	both modified:   simple_subscription/simple_subscription/doctype/simple_subscription/test_simple_subscription.py

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