Test with supported logstash versions

Author: whyscream

.github/workflows/test_config_syntax.yml

@@ -3,11 +3,18 @@ on: [push, workflow_dispatch]
 jobs:
   test-syntax:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        logstash-version: ['8.14.1', '7.17.22']
     steps:
-      - uses: actions/checkout@v4
-      - run: |
+      - name: Checkout code
+        uses: actions/checkout@v4
+      - name: Validate configuration syntax
+        env:
+          LOGSTASH_VERSION: ${{matrix.logstash-version}}
+        run: |
           docker run --rm \
           --volume ./postfix.grok:/etc/logstash/patterns.d/postfix.grok \
           --volume ./50-filter-postfix.conf:/usr/share/logstash/pipeline/50-filter-postfix.conf \
-          logstash:8.12.0 \
+          logstash:${LOGSTASH_VERSION} \
           logstash --config.test_and_exit -f /usr/share/logstash/pipeline/50-filter-postfix.conf