ci: add PostgreSQL version matrix for CI testing

Run full test suite against PostgreSQL 14, 15, 16, 17, and 18 in parallel.
PG_VERSION env var allows version selection with default of 17.

Author: tobyhede

.github/workflows/test.yml

@@ -13,8 +13,14 @@ env:
 
 jobs:
   test:
-    name: Test
+    name: Test (PostgreSQL ${{ matrix.pg_version }})
     runs-on: blacksmith-16vcpu-ubuntu-2204
+    strategy:
+      fail-fast: false
+      matrix:
+        pg_version: [14, 15, 16, 17, 18]
+    env:
+      PG_VERSION: ${{ matrix.pg_version }}
     steps:
       - uses: actions/checkout@v4
       - uses: ./.github/actions/setup-test

tests/docker-compose.yml

@@ -1,6 +1,6 @@
 services:
   postgres: &postgres
-    image: postgres:17
+    image: postgres:${PG_VERSION:-17}
     pull_policy: always
     container_name: postgres
     command: -c 'config_file=/etc/postgresql/postgresql.conf'
@@ -32,7 +32,7 @@ services:
 
   postgres-17-tls:
     <<: *postgres
-    image: postgres:17
+    image: postgres:${PG_VERSION:-17}
     container_name: postgres-17-tls
     environment:
       PGPORT: 5617