feat(billing): inbound API handlers (customer/usage/catalog)

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

fusion_centralize_billing/models/service.py

@@ -62,3 +62,34 @@ class FusionBillingService(models.Model):
             return self.browse()
         key_hash = hashlib.sha256(raw_key.encode()).hexdigest()
         return self.search([('api_key_hash', '=', key_hash), ('active', '=', True)], limit=1)
+
+    def _api_upsert_customer(self, payload):
+        self.ensure_one()
+        ext = payload.get('external_id')
+        if not ext:
+            return {'status': 'error', 'error': 'external_id required'}
+        link = self.env['fusion.billing.account.link']._resolve_or_create_partner(
+            self, ext, name=payload.get('name'), email=payload.get('email'))
+        return {'status': 'ok', 'partner_id': link.partner_id.id, 'external_id': ext}
+
+    def _api_record_usage(self, payload):
+        self.ensure_one()
+        events = payload.get('events') or []
+        Usage = self.env['fusion.billing.usage']
+        accepted = 0
+        for ev in events:
+            sub = self.env['sale.order'].browse(int(ev['subscription_external_id']))
+            Usage._record_usage(
+                sub, ev['metric_code'], float(ev['quantity']),
+                ev['period_start'], ev['period_end'], idem=ev.get('idempotency_key'))
+            accepted += 1
+        return {'status': 'ok', 'accepted': accepted}
+
+    def _api_catalog(self):
+        self.ensure_one()
+        charges = self.env['fusion.billing.charge'].search([('active', '=', True)])
+        return {'status': 'ok', 'charges': [{
+            'plan_code': c.plan_code, 'metric': c.metric_id.code,
+            'included_quota': c.included_quota, 'price_per_unit': c.price_per_unit,
+            'unit_batch': c.unit_batch, 'charge_model': c.charge_model,
+        } for c in charges]}