Add plan with optional params

plans/optional_target.pp

@@ -0,0 +1,7 @@
+# A plan that has an optional targetspec param
+# @param targets Targets to run the first task against.
+plan teams_ui_bolt_project::optional_target(Optional[TargetSpec] $targets) {
+  out::message('Test output message')
+
+  return 'Plan completed'
+}