Add an IAM policy so the DynamoDB table can be scanned

template.yaml

Resources:
  HelloWorldFunction:
    Type: AWS::Serverless::Function
    Properties:
      CodeUri: hello_world/
      Handler: app.lambda_handler
      Runtime: python3.8
      Environment:
        Variables:
          TABLE_NAME: !Ref MyTable
      # grant permission to the table using a policy template
      Policies:
        - DynamoDBReadPolicy
            TableName: !Ref MyTable