Split building the demo image

This doesn't need to be kept exactly in sync with master

.github/workflows/docker-base.yml

@@ -1,9 +1,11 @@
 name: Build and push base Docker images
 
+# Only build when the dockerfile has changed, otherwise scheduled on the first
+# of each month
 on:
   push:
     branches:
-      - "master"
+      '- "master"'
     paths:
       - 'extras/docker/base/Dockerfile'
       - '.github/workflows/docker-base.yml'

.github/workflows/docker-demo.yml

@@ -0,0 +1,43 @@
+name: Build and push demo Docker image
+
+# Only build when the dockerfile has changed, otherwise scheduled every two weeks
+# (on the 1st and 15th every month) since it's not so important to keep this image
+# exactly in sync with master
+on:
+  push:
+    branches:
+      - 'master'
+    paths:
+      - 'extras/docker/demo/Dockerfile'
+      - '.github/workflows/docker-demo.yml'
+  schedule:
+    - cron: '0 6 1,15 * *'
+
+jobs:
+  demo:
+    name: Build demo image
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v2.2.0
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v2.9.0
+
+      - name: Login to DockerHub
+        uses: docker/login-action@v2.2.0
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Build image
+        uses: docker/build-push-action@v4.1.0
+        with:
+          context: .
+          push: true
+          file: extras/docker/demo/Dockerfile
+          platforms: linux/amd64,linux/arm64
+          tags: wger/demo:latest,wger/demo:2.2-dev,wger/apache:latest,wger/apache:2.2-dev

.github/workflows/docker.yml

@@ -1,5 +1,5 @@
 #  https://docs.docker.com/build/ci/github-actions/multi-platform/
-name: Build and push Docker images
+name: Build and push production Docker images
 
 on:
   push:
@@ -11,34 +11,6 @@ env:
   REGISTRY_IMAGE_ALT: wger/devel
 
 jobs:
-  demo:
-    name: Build demo image
-    runs-on: ubuntu-latest
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v3
-
-      - name: Set up QEMU
-        uses: docker/setup-qemu-action@v2.2.0
-
-      - name: Set up Docker Buildx
-        uses: docker/setup-buildx-action@v2.9.0
-
-      - name: Login to DockerHub
-        uses: docker/login-action@v2.2.0
-        with:
-          username: ${{ secrets.DOCKERHUB_USERNAME }}
-          password: ${{ secrets.DOCKERHUB_TOKEN }}
-
-      - name: Build image
-        uses: docker/build-push-action@v4.1.0
-        with:
-          context: .
-          push: true
-          file: extras/docker/demo/Dockerfile
-          platforms: linux/amd64,linux/arm64
-          tags: wger/demo:latest,wger/demo:2.2-dev,wger/apache:latest,wger/apache:2.2-dev
-
   build-prod:
     name: Build production image
     runs-on: ubuntu-latest