Create scaffolding of ddl-simulator

Implement global server as control plane

Implement device to get their info from global server and connect each
others

pkg/leader/tree.go

@@ -0,0 +1,17 @@
+package leader
+
+type TreeNode struct {
+	Id       string     `yaml:"id"`
+	Children []TreeNode `yaml:"children,omitempty"`
+}
+
+func NewTreeNode(id string, children []TreeNode) *TreeNode {
+	return &TreeNode{
+		Id:       id,
+		Children: children,
+	}
+}
+
+func (t *TreeNode) AddChild(child *TreeNode) {
+	t.Children = append(t.Children, *child)
+}