The source of the AWS credential. The credential source map must contain the
regional_cred_verification_url field.
The regional_cred_verification_url is the regional GetCallerIdentity action URL, used to
determine the account ID and its roles.
The environment_id is the environment identifier, in the format “aws${version}”. This
indicates whether breaking changes were introduced to the underlying AWS implementation.
The region_url identifies the targeted region. Optional.
The url locates the metadata server used to retrieve the AWS credentials. Optional.