fix: invoice pending lines via charges

[turip]

Overview

When credits enabled we need to use charges to invoke InvoicePendingLines until the refactored billing worker's in place.

This patch makes sure that we are using the right backend.

Notes for reviewer

Summary by CodeRabbit

• Refactor

  • Split invoice pending-lines handling into its own service and updated billing wiring across the server and billing components to improve separation of concerns.

• Tests

  • Updated test setups and configurations to reflect the new billing service wiring.

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds an InvoicePendingLinesService interface and threads it through billing registry, HTTP handlers, workers, router, server, and tests; refactors consumers to call the new dedicated service instead of the broader billing service.

Changes

Cohort / File(s)	Summary
Service Interfaces openmeter/billing/service.go, openmeter/billing/charges/service.go	Added InvoicePendingLinesService; InvoiceService now embeds it. GatheringInvoiceService gains RecalculateGatheringInvoices.
Registry & Server Bootstrap app/common/billing.go, cmd/server/main.go	Added BillingRegistry.InvoicePendingLinesService() and wired its result into server/router bootstrap.
HTTP Handler openmeter/billing/httpdriver/handler.go, openmeter/billing/httpdriver/invoice.go	Handler now accepts invoicePendingLinesService and InvoicePendingLinesAction calls the dedicated service instead of the general billing service.
Invoice Collector Worker openmeter/billing/worker/collect/collect.go	Replaced single billing.Service dependency with GatheringInvoiceService and InvoicePendingLinesService; rewired list/collect fallback calls accordingly.
Subscription Sync Worker openmeter/billing/worker/subscriptionsync/service/service.go, .../sync.go, .../base_test.go	Config and service now require InvoicePendingLinesService; code paths switched to use the new dependency. Tests updated to provide the new field.
Router & Tests openmeter/server/router/router.go, openmeter/server/server_test.go, test/.../framework_test.go, test/billing/subscription_test.go	Router config extended with BillingInvoicePendingLines; server and test fixtures wired to supply the new dependency.

Sequence Diagram(s)

(Skipped — changes are wiring/refactor without introducing a new multi-component runtime flow that benefits from sequence visualization.)

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• feat: add wire for charges #4058 — prior changes to BillingRegistry wiring that this PR extends by adding InvoicePendingLinesService integration.

Suggested labels

release-note/misc, area/billing

Suggested reviewers

• tothandras

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 11.11% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The PR title 'fix: invoice pending lines via charges' clearly summarizes the main change: enabling InvoicePendingLines to be invoked via the charges backend when credits are enabled, which is the core objective of this PR.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/invoice-pending-lines

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[coderabbitai]

🧹 Nitpick comments (1)

openmeter/billing/service.go (1)

98-100: RecalculateGatheringInvoices is declared in both InvoiceService and GatheringInvoiceService.

This method appears in both interfaces (lines 98-100 and line 126). Since Service embeds both, this works fine, but it's a bit redundant. If this is intentional (e.g., allowing consumers to depend on either interface), that's cool! If not, you might want to keep it in just one place.

Also applies to: 126-126

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@openmeter/billing/service.go` around lines 98 - 100, The
RecalculateGatheringInvoices method is duplicated in both InvoiceService and
GatheringInvoiceService; decide which interface should own it (e.g., keep it
only in GatheringInvoiceService or only in InvoiceService) and remove the
redundant declaration from the other interface so Service still inherits it by
embedding the correct interface; update any docs/comments to reflect the single
source of truth and ensure callers reference the chosen interface name
(RecalculateGatheringInvoices, InvoiceService, GatheringInvoiceService, Service)
accordingly.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@openmeter/billing/service.go`:
- Around line 98-100: The RecalculateGatheringInvoices method is duplicated in
both InvoiceService and GatheringInvoiceService; decide which interface should
own it (e.g., keep it only in GatheringInvoiceService or only in InvoiceService)
and remove the redundant declaration from the other interface so Service still
inherits it by embedding the correct interface; update any docs/comments to
reflect the single source of truth and ensure callers reference the chosen
interface name (RecalculateGatheringInvoices, InvoiceService,
GatheringInvoiceService, Service) accordingly.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 9a0b1f4a-f51b-414a-8591-7468c1b3ca00

📥 Commits

Reviewing files that changed from the base of the PR and between 767cd9e and c8546e4.

📒 Files selected for processing (14)

• app/common/billing.go
• cmd/server/main.go
• openmeter/billing/charges/service.go
• openmeter/billing/httpdriver/handler.go
• openmeter/billing/httpdriver/invoice.go
• openmeter/billing/service.go
• openmeter/billing/worker/collect/collect.go
• openmeter/billing/worker/subscriptionsync/service/base_test.go
• openmeter/billing/worker/subscriptionsync/service/service.go
• openmeter/billing/worker/subscriptionsync/service/sync.go
• openmeter/server/router/router.go
• openmeter/server/server_test.go
• test/billing/subscription_test.go
• test/subscription/framework_test.go

✅ Files skipped from review due to trivial changes (2)

• openmeter/billing/worker/subscriptionsync/service/base_test.go
• openmeter/billing/charges/service.go

🚧 Files skipped from review as they are similar to previous changes (8)

• test/billing/subscription_test.go
• test/subscription/framework_test.go
• openmeter/server/server_test.go
• openmeter/billing/httpdriver/handler.go
• openmeter/server/router/router.go
• app/common/billing.go
• openmeter/billing/worker/subscriptionsync/service/service.go
• openmeter/billing/worker/collect/collect.go