Ensure flyway migrations are not changed (and validate them)

.github/workflows/flyway-check.yml

@@ -0,0 +1,45 @@
+name: Flyway Migration Check
+
+on:
+  pull_request:
+    branches: [ main ]
+    paths:
+      - 'src/main/resources/db/migration/**'
+
+jobs:
+  check-migrations:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v3
+      with:
+        fetch-depth: 0
+
+    - name: Set up JDK 11
+      uses: actions/setup-java@v3
+      with:
+        java-version: '11'
+        distribution: 'adopt'
+
+    - name: Install Flyway CLI
+      run: |
+        wget -qO- https://repo1.maven.org/maven2/org/flywaydb/flyway-commandline/8.5.13/flyway-commandline-8.5.13-linux-x64.tar.gz | tar xvz
+        sudo ln -s `pwd`/flyway-8.5.13/flyway /usr/local/bin
+
+    - name: Check for modified migrations
+      run: |
+        git diff --name-only origin/main...HEAD -- backend/src/main/resources/db/migration/ > changed_files.txt
+        if [ -s changed_files.txt ]; then
+          echo "The following migration files have been modified:"
+          cat changed_files.txt
+          echo "Error: Modifying existing migrations is not allowed."
+          exit 1
+        else
+          echo "No existing migrations have been modified."
+        fi
+
+    - name: Validate new migrations
+      run: flyway validate -locations=filesystem:backend/src/main/resources/db/migration
+
+    - name: Run Flyway info
+      run: flyway info -locations=filesystem:backend/src/main/resources/db/migration