openapi: 3.1.0
info:
  title: Callback refd
  version: 1.2.3
paths:
  /trans:
    post:
      description: ''
      requestBody:
        description: ''
        content:
          'application/json':
            schema:
              properties:
                id: {type: string}
                email: {format: email}
      responses:
        '201':
          description: subscription successfully created
          content:
            application/json:
              schema:
                type: object
      callbacks:
        transactionCallback:
          'http://notificationServer.com?transactionId={$request.body#/id}&email={$request.body#/email}':
            $ref: callback-transactioned.yml

  /other:
    post:
      description: ''
      parameters:
      - name: queryUrl
        in: query
        required: true
        description: |
          bla
          bla
          bla
        schema:
          type: string
          format: uri
          example: https://example.com
      responses:
        '201':
          description: ''
          content:
            application/json:
              schema:
                type: object
      callbacks:
        myEvent:
          $ref: '#/components/callbacks/MyCallbackEvent'

components:
  schemas:
    SomePayload: {type: object}
    SomeOtherPayload: {type: boolean}
  callbacks:
    MyCallbackEvent:
      '{$request.query.queryUrl}':
        post:
          requestBody:
            description: Callback payload
            content:
              'application/json':
                schema:
                  $ref: '#/components/schemas/SomeOtherPayload'
          responses:
            '200':
              description: callback successfully processed