导入FUNCTION类型后端服务API

包含IAM认证和请求参数编排的GET方法API定义，后端服务类型为FunctionGraph。

Swagger示例：

swagger: "2.0"
info:
  title: "importFunctionEndpoint"
  description: "import apis"
  version: "1.0"
host: "api.account.com"
paths:
  '/function/{name}':
    get:
      operationId: "invokeFunction"
      description: "invoke function by name"
      security:
      - apig-auth-iam: []
      schemes:
      - https
      parameters:
      - name: "test"
        description: "authorization token"
        type: "string"
        in: "header"
        required: true
      - name: "name"
        description: "function name"
        type: "string"
        in: "path"
        required: true
      responses:
        "200":
          description: "function result"
      x-apigateway-request-type: "public"
      x-apigateway-cors: true
      x-apigateway-match-mode: "NORMAL"
      x-apigateway-backend:
        type: "FUNCTION"
        parameters:
        - name: "functionName"
          value: "name"
          in: "query"
          origin: "REQUEST"
          description: "funtion name"
        - name: "X-Invoke-User"
          value: "apigateway"
          in: "header"
          origin: "CONSTANT"
          description: "invoke user"
        functionEndpoints:
          function-urn: "your function urn address"
          version: "your function version"
          invocation-type: "async"
          timeout: 30000
securityDefinitions:
  apig-auth-app:
    in: header
    name: Authorization
    type: apiKey
    x-apigateway-auth-type: AppSigv1
  apig-auth-iam:
    in: header
    name: unused
    type: apiKey
    x-apigateway-auth-type: IAM