Add scheduled workflow to clean untagged images

.github/workflows/clean_untagged.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+set -e
+
+
+image_names=(
+	"devcontainer-build-run-devcontainer"
+	"devcontainer-build-run/tests/run-args"
+	"devcontainer-build-run/tests/build-args"
+	"devcontainer-build-run/tests/dockerfile-context"
+	"devcontainer-build-run/tests/feature-docker-from-docker"
+	"devcontainer-build-run/tests/docker-from-docker-non-root"
+	"devcontainer-build-run/tests/docker-from-docker-root"
+	"devcontainer-build-run/tests/skip-user-update"
+)
+
+for image_name in ${image_names[@]}; 
+do
+	echo "Checking for untagged versions for $image_name"
+	escaped_image_name=$(echo ${image_name} | sed "s/\//%2f/g")
+	version_ids=$(curl -s  -H "Authorization: Bearer $GITHUB_TOKEN"  -H "Accept: application/vnd.github.v3+json" "https://api.github.com/users/stuartleeks/packages/container/$escaped_image_name/versions?per_page=100" | jq -r ".[] | select(.metadata.container.tags | length ==0) | .id")
+	for version_id in ${version_ids[@]}; 
+	do
+		echo -e "\tDeleting version '$version_id' for '$image_name:$tag' ..."
+		curl -s -X DELETE -H "Authorization: Bearer $GITHUB_TOKEN"  -H "Accept: application/vnd.github.v3+json" "https://api.github.com/users/stuartleeks/packages/container/$escaped_image_name/versions/$version_id"
+	done
+done

.github/workflows/untagged-image-cleanup.yml

@@ -0,0 +1,23 @@
+name: untagged_image_cleanup
+
+on:  # yamllint disable-line rule:truthy
+  schedule:
+    - cron: "4 18 * * *"
+  workflow_dispatch:
+
+jobs:
+
+  clean_images:
+    name: 
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+        with:
+          persist-credentials: false
+
+      - name: Clean untagged GitHub container images
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        run:
+          ./.github/workflows/clean_untagged.sh