Pagination error of Apigee (OpenAPI) integration

[w_inoue_yata]

I'd like to access huge data located in external system from my AppSheet app so now trying to use OpenAPI integration. I don't want to build an Apigee instance which is quite expensive just for this use case, so I simply created a public REST API on Cloud Run and served OpenAPI spec on (https://{hostname}/apispec.yaml) and added it as an Apigee API connection. It worked well as I expected.

openapi: 3.0.3
info:
  description: API for managing Products.
  version: 0.0.1
  title: Products API
servers:
- url: https://openapi-sample-xxxx.a.run.app/
security:
  - ApiKeyAuth: [] 
paths:
  /products:
    get:
      summary: List 'Products' objects.
      description: Retrieve a page of 'Product' objects from the server. 
      responses:
        "200":
          description: Successful response
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Product'
    post:
      ...(omit)...
components:
  securitySchemes:
    ApiKeyAuth:
      type: apiKey
      name: x-apikey
      in: header
  schemas:
    Product:
      title: Product
      type: object
      properties:
        created_at:
          type: string
        department_name:
          type: string
        id:
          type: string
        image:
          type: string
        jan:
          type: string
        list_price:
          type: integer

Next, as the number of records are so huge, I need to support pagination. So I implemented limit&offset based pagination on GET /products endpoint, and added the x-pagination section to the yaml following the official doc. 

After that I tried to add the integration information on AppSheet console, but when I press validate button, it showed the following error:

Error
Not connected. Invalid OpenAPI Spec: Apigee: Invalid pagination

Does anyone has any advice? The current yaml which causes error is the following:

openapi: 3.0.3
info:
  description: API for managing Products.
  version: 0.0.1
  title: Products API
servers:
- url: https://openapi-sample-xxxx.a.run.app/
security:
  - ApiKeyAuth: [] 
paths:
  /products:
    get:
      summary: List 'Products' objects.
      description: Retrieve a page of 'Product' objects from the server. 
      responses:
        "200":
          description: Successful response
          content:
            application/json:
              schema:
                type: array
                items:
                  $ref: '#/components/schemas/Product'
      x-pagination:
        type: offset
        limitParam: limit
        defaulLimit: 100
        offsetParam: offset
        defaultOffset: 0
    post:
      ...(omit)...
components:
  securitySchemes:
    ApiKeyAuth:
      type: apiKey
      name: x-apikey
      in: header
  schemas:
    Product:
      title: Product
      type: object
      properties:
        created_at:
          type: string
        department_name:
          type: string
        id:
          type: string
        image:
          type: string
        jan:
          type: string
        list_price:
          type: integer