Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: s3://bucket/key
      Handler: app.handler
      Runtime: nodejs14.x
      Events:
        CognitoUserPoolPreSignup:
          Type: Cognito
          Properties:
            UserPool:
              Ref: MyCognitoUserPool
            Trigger: PreSignUp

  MyCognitoUserPool:
    Type: AWS::Cognito::UserPool
    Properties:
      UserPoolName: PreSignup
      SmsConfiguration:
        SnsCallerArn: !GetAtt UserPoolRole.Arn
        ExternalId: !Ref ExternalId