feat(billing): idempotent usage ingestion

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

fusion_centralize_billing/models/usage.py

@@ -1,7 +1,7 @@
 # -*- coding: utf-8 -*-
 # Copyright 2026 Nexa Systems Inc.
 # License OPL-1
-from odoo import fields, models
+from odoo import api, fields, models
 
 
 class FusionBillingUsage(models.Model):
@@ -37,3 +37,24 @@ class FusionBillingUsage(models.Model):
     _idempotency_uniq = models.Constraint(
         "unique(idempotency_key)", "Usage idempotency key must be unique.",
     )
+
+    @api.model
+    def _record_usage(self, subscription, metric_code, quantity, period_start, period_end, idem=None):
+        """Upsert one aggregated usage row. Same idempotency key updates in place (no double-count)."""
+        metric = self.env['fusion.billing.metric'].search([('code', '=', metric_code)], limit=1)
+        if not metric:
+            raise ValueError("Unknown metric code: %s" % metric_code)
+        vals = {
+            'subscription_id': subscription.id,
+            'metric_id': metric.id,
+            'period_start': period_start,
+            'period_end': period_end,
+            'quantity': quantity,
+            'idempotency_key': idem,
+        }
+        if idem:
+            existing = self.search([('idempotency_key', '=', idem)], limit=1)
+            if existing:
+                existing.write({'quantity': quantity})
+                return existing
+        return self.create(vals)