ci: add workflow to check if there are missing migrations

Closes: #1263

.github/workflows/django-migrations.yml

@@ -0,0 +1,25 @@
+#SPDX-FileCopyrightText: 2024 Birger Schacht
+#SPDX-License-Identifier: MIT
+
+name: Check if there are missing migrations
+on:
+  pull_request:
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      # for poetry caching, we have to install poetry before setting up python
+      - name: Install poetry
+        run: pipx install poetry
+      - uses: actions/setup-python@v5
+        with:
+          cache: 'poetry'
+          cache-dependency-path: "pyproject.toml"
+          python-version: "3.11"
+      - name: Install project
+        run: |
+          poetry install
+      - name: Make migrations
+        run: poetry run ./manage.py makemigrations | grep "No changes detected"