refactor(billing): Billing simplification entitlement usage

[whoAbhishekSah]

Summary

Simplify billing entitlement and usage APIs by automatically inferring billing_id from org_id. Clients now only need to provide org_id when calling these RPCs.

Changes

Proto Updates

• Deprecated billing_id and project_id fields in:
  • CheckFeatureEntitlementRequest
  • CreateBillingUsageRequest
  • RevertBillingUsageRequest
• Updated proton ref to 4144445eb0f9cbd1a801a3d0aa5cfce4cc0ea551

Backend Updates

All handlers now always fetch billing_id from org_id:

• CheckFeatureEntitlement: Uses customerService.GetByOrgID()
• CreateBillingUsage: Uses customerService.GetByOrgID()
• RevertBillingUsage: Uses customerService.GetByOrgID()

Removed ensureBillingAccountBelongToOrg validation from CreateBillingUsage authorization interceptor (now redundant).

Error Handling

• ErrNotFound: Empty response for CheckFeatureEntitlement, CodeNotFound for others
• ErrInvalidUUID/ErrInvalidID: CodeInvalidArgument
• Other errors: CodeInternal with logging

Benefits

• Simpler API: Single required parameter (org_id)
• More secure: Users cannot provide arbitrary billing_id
• Consistent: Same behavior across all requests
• Cleaner code: No conditional logic for inferring billing_id

Breaking Changes

None - deprecated fields are still accepted for backward compatibility but ignored.

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Project	Deployment	Preview	Comments	Updated (UTC)
frontier	Ready	Preview	Comment	Dec 4, 2025 5:01am

[coveralls]

Pull Request Test Coverage Report for Build 19918211554

Details

• 18 of 45 (40.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.001%) to 37.645%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
internal/api/v1beta1connect/billing_check.go	12	15	80.0%
internal/api/v1beta1connect/billing_usage.go	6	30	20.0%
<!--	Total:	18	45

Totals
Change from base Build 19819539745:	0.001%
Covered Lines:	15705
Relevant Lines:	41719

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💛 - Coveralls