fix(ledger): book advance attribution at purchase time

[GAlexIHU]

Summary

• keep subscription and schedule definitions ledger-neutral; this changes only the materialized credit-purchase initiation path
• determine and book existing advance attribution at purchase time
• keep only the non-attributed remainder as issuance at the grant's future effective_at
• align the ledger timing with the immediate lineage backfill so a subsequent committed purchase sees the already-settled advance

Behavior

• a future-effective 100-credit purchase against 40 of existing advance books 40 of attribution immediately and 60 of issuance at effective_at
• the future 60 does not appear in the current spendable balance
• two sequential 60-credit purchases against 100 of advance attribute 60 + 40, with only the remaining 20 issued in the future
• promotional purchase coverage verifies that grant realization and lineage use the same purchase-time ledger transaction group

Invoice-settled purchases keep their existing trigger at invoice draft creation. This PR does not add payment control or recurring subscription grants.

Cancellation / void limitation

The existing void path operates on currently issued future-balance-overage value for the source charge. Before a future grant reaches effective_at, its scheduled remainder has no spendable balance slice to void, and the purchase-time advance attribution is not such a slice. As a result, future-effective grants remain non-voidable before effective_at; this PR does not add cancellation of scheduled ledger entries or claim to solve that lifecycle. Void behavior for remaining issued value after effective_at is unchanged.

Tests

• nix develop --impure .#ci -c env POSTGRES_HOST=127.0.0.1 go vet -tags=dynamic ./openmeter/ledger/chargeadapter ./openmeter/billing/charges/creditpurchase/service
• nix develop --impure .#ci -c env POSTGRES_HOST=127.0.0.1 go test -tags=dynamic -v ./openmeter/ledger/chargeadapter ./openmeter/billing/charges/creditpurchase/service
• nix develop --impure .#ci -c env POSTGRES_HOST=127.0.0.1 go test -tags=dynamic -v ./test/credits

All database-backed tests ran against PostgreSQL; none were skipped.

Greptile Summary

This PR books existing advance attribution when a credit purchase is materialized. The main changes are:

• Advance attribution and accrued-cost translation move to purchase time.
• Remaining credit issuance stays at the grant effective time.
• Tests cover future-effective grants, sequential purchases, and promotional lineage timing.

Confidence Score: 4/5

Past-effective promotional purchases need a ledger-ordering fix before merging.

• Future-effective purchases consume advance at the intended time.
• Past-effective purchases can place authorization and settlement before the newly moved attribution.
• The added tests do not cover this timing order.

openmeter/ledger/chargeadapter/creditpurchase.go

Important Files Changed

Filename	Overview
openmeter/ledger/chargeadapter/creditpurchase.go	Splits attribution and issuance timestamps, but past-effective promotional purchases can record settlement before attribution.
openmeter/ledger/chargeadapter/creditpurchase_test.go	Adds database-backed coverage for future-effective grants and sequential advance consumption.
openmeter/billing/charges/creditpurchase/service/promotional_test.go	Verifies that promotional realization and lineage use the purchase-time transaction group.

Sequence Diagram

%%{init: {'theme': 'neutral'}}%%
sequenceDiagram
    participant C as Purchase caller
    participant H as Credit purchase handler
    participant L as Ledger
    C->>H: Materialize past-effective promotional purchase
    H->>L: Authorize and settle at effectiveAt
    H->>L: Attribute advance at purchasedAt
    Note over L: Settlement appears before attribution in ledger history

Loading

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sequenceDiagram
    participant C as Purchase caller
    participant H as Credit purchase handler
    participant L as Ledger
    C->>H: Materialize past-effective promotional purchase
    H->>L: Authorize and settle at effectiveAt
    H->>L: Attribute advance at purchasedAt
    Note over L: Settlement appears before attribution in ledger history

Loading

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
openmeter/ledger/chargeadapter/creditpurchase.go:242
**Past-Effective Settlement Precedes Attribution**

When a promotional purchase is materialized after its `effectiveAt`, this attribution is booked at the current time while authorization and settlement remain booked at the earlier effective time. An as-of query between those times therefore shows the purchase settled before its receivable attribution exists, producing invalid ledger history for a supported past-effective charge.

_{Reviews (1): Last reviewed commit: "fix(ledger): book advance attribution at..." | Re-trigger Greptile}

Greptile also left 1 inline comment on this PR.

Context used:

• Context used - CLAUDE.md (source)
• Context used - AGENTS.md (source)

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[greptile-apps]

Past-Effective Settlement Precedes Attribution

When a promotional purchase is materialized after its effectiveAt, this attribution is booked at the current time while authorization and settlement remain booked at the earlier effective time. An as-of query between those times therefore shows the purchase settled before its receivable attribution exists, producing invalid ledger history for a supported past-effective charge.

Prompt To Fix With AI

This is a comment left during a code review.
Path: openmeter/ledger/chargeadapter/creditpurchase.go
Line: 242

Comment:
**Past-Effective Settlement Precedes Attribution**

When a promotional purchase is materialized after its `effectiveAt`, this attribution is booked at the current time while authorization and settlement remain booked at the earlier effective time. An as-of query between those times therefore shows the purchase settled before its receivable attribution exists, producing invalid ledger history for a supported past-effective charge.

How can I resolve this? If you propose a fix, please make it concise.