Split up steps and implement license management

action/steps/return_license.sh

@@ -0,0 +1,16 @@
+#!/usr/bin/env bash
+
+if [[ -n "$UNITY_SERIAL" ]]; then
+  #
+  # PROFESSIONAL (SERIAL) LICENSE MODE
+  #
+  # This will return the license that is currently in use.
+  #
+  xvfb-run --auto-servernum --server-args='-screen 0 640x480x24' \
+    /opt/Unity/Editor/Unity \
+      -batchmode \
+      -nographics \
+      -logFile /dev/stdout \
+      -quit \
+      -returnlicense
+fi