Specifies a unique, case-sensitive identifier that you provide to ensure the idempotency of the request. This lets you safely retry the request without accidentally performing the same operation a second time. Passing the same value to a later call to an operation requires that you also pass the same value for all other parameters. We recommend that you use a UUID type of value..
If you don't provide this value, then Amazon Web Services generates a random one for you.
The Amazon Resoure Name (ARN) of the invitation that you want to accept.