Returns the Amazon Resource Name (ARN) for the certificate. For example: { "Fn::GetAtt": ["MyCertificate", "Arn"] } A value similar to the following is returned: arn:aws:iot:ap-southeast-2:123456789012:cert/a1234567b89c012d3e4fg567hij8k9l01mno1p23q45678901rs234567890t1u2