[Update OpenAPI] Merge openapi: added Billing Portal API PROD (#426)

Co-authored-by: manuraf <12083207+manuraf@users.noreply.github.com>

infra/apim_v2/api/billing-portal-api/v1/openapi.prod.json

@@ -0,0 +1,26 @@
+{
+  "openapi": "3.0.3",
+  "info": {
+    "title": "Billing Portal API service",
+    "description": "This service is the proxy for the billing portal",
+    "version": "1.0.0"
+  },
+  "servers": [
+    {
+      "url": "https://${host}/${basePath}"
+    }
+  ],
+  "tags": [],
+  "paths": {},
+  "components": {
+    "schemas": {},
+    "securitySchemes": {
+      "bearerAuth": {
+        "type": "http",
+        "description": "A bearer token in the format of a JWS and conformed to the specifications included in [RFC8725](https://tools.ietf.org/html/RFC8725)",
+        "scheme": "bearer",
+        "bearerFormat": "JWT"
+      }
+    }
+  }
+}