Unit 2.5 Section 3: Create API in Amazon API Gateway, The "TopicARN" should be "TopicArn"

[JunyanHe]

Name: Message – Mapped from: method.request.header.message Name: Subject – Mapped from: method.request.header.subject Name: TopicARN – Mapped from: method.request.header.topic

The last line should be "Name: TopicArn – Mapped from: method.request.header.topic". Otherwise we will get an error : "Message": "Invalid parameter: TopicArn or TargetArn Reason: no value for required parameter".