docker: Authenticate to ECS

For the local docker daemon to connect to an AWS ECS container registry, you must supply credentials:

• username = AWS
• password = aws ecr get-login-password ...

Try a command like the following:

export AWS_ACCOUNT="<your-account-id>"
export AWS_REGION="ap-southeast-2" # etc.
aws ecr get-login-password --region "${AWS_REGION}" \
  |  docker login --username AWS --password-stdin "${AWS_ACCOUNT}.dkr.ecr.${AWS_REGION}.amazonaws.com"