AWS Access Key used to manage the Amazon ECS cluster.

If no AWS Access Key is set, implicit authentication mechanisms are used:

• Environment Variables - AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY (RECOMMENDED since they are recognized by all the AWS SDKs and CLI except for .NET), or AWS_ACCESS_KEY and AWS_SECRET_KEY (only recognized by Java SDK)
• Java System Properties - aws.accessKeyId and aws.secretKey
• Credential profiles file at the default location (~/.aws/credentials) shared by all AWS SDKs and the AWS CLI
• Instance profile credentials delivered through the Amazon EC2 metadata service (IAM role defined at the ec2 instance level)