IAM.UserToGroupAddition
see http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-iam-addusertogroup.html
see http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-properties-iam-addusertogroup.html;
val make_properties :
group_name:string ->
users:string list ->
unit ->
properties
val yojson_of_properties :
properties ->
[> `Assoc of (string * Yojson.Safe.t) list ]
val create_attributes : string -> attributes