ci: add check to identify number of stable versions deployed (#532)

Co-authored-by: yuroitaki <t.kleinchong@gmail.com>

cd-scripts/appspec-scripts/before_install.sh

@@ -3,7 +3,15 @@ set -e
 
 APP_NAME=$(echo $APPLICATION_NAME | awk -F- '{ print $2 }')
 
-if [ $APP_NAME = "nightly" ]; then
+if [ $APP_NAME = "stable" ]; then
+  VERSIONS_DEPLOYED=$(find ~/ -maxdepth 1 -type d -name 'stable_*')
+  VERSIONS_DEPLOYED_COUNT=$(echo $VERSIONS_DEPLOYED | wc -w)
+
+  if [ $VERSIONS_DEPLOYED_COUNT -gt 3 ]; then
+    echo "More than 3 stable versions found"
+    exit 1
+  fi
+else
   if [ ! -d ~/$APP_NAME ]; then
     mkdir ~/$APP_NAME
   fi