updates CI workflow file.

- apply temporary fix for broken NVM
- add postgres to test matrix
- reduce moodle environments down to M4.3
- version bump on checkout action

.github/workflows/ci.yml

@@ -4,7 +4,7 @@ on:
   push:
   pull_request:
   schedule:
-    - cron: '33 2 * * 1' # weekly, on Monday morning
+    - cron: "33 2 * * 1" # weekly, on Monday morning
 env:
   SLACK_WEBHOOK_URL: ${{ secrets.SLACK_ILIOS_DEPLOYMENT_WEBHOOK_URL }}
 
@@ -13,10 +13,19 @@ jobs:
     runs-on: ubuntu-latest
 
     services:
+      postgres:
+        image: postgres:13
+        env:
+          POSTGRES_USER: "postgres"
+          POSTGRES_HOST_AUTH_METHOD: "trust"
+        ports:
+          - 5432:5432
+        options: --health-cmd pg_isready --health-interval 10s --health-timeout 5s --health-retries 3
+
       mariadb:
         image: mariadb:10
         env:
-          MYSQL_USER: 'root'
+          MYSQL_USER: "root"
           MYSQL_ALLOW_EMPTY_PASSWORD: "true"
           MYSQL_CHARACTER_SET_SERVER: "utf8mb4"
           MYSQL_COLLATION_SERVER: "utf8mb4_unicode_ci"
@@ -27,19 +36,13 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        include:
-          - php: '8.3'
-            moodle-branch: 'main'
-            database: 'mariadb'
-          - php: '8.3'
-            moodle-branch: 'MOODLE_404_STABLE'
-            database: 'mariadb'
-          - php: '8.2'
-            moodle-branch: 'MOODLE_403_STABLE'
-            database: 'mariadb'
+        php: ["8.1", "8.2"]
+        moodle-branch: ["MOODLE_403_STABLE"]
+        database: [pgsql, mariadb]
+
     steps:
       - name: Check out repository code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           path: plugin
 
@@ -59,7 +62,9 @@ jobs:
           echo $(cd ci/bin; pwd) >> $GITHUB_PATH
           echo $(cd ci/vendor/bin; pwd) >> $GITHUB_PATH
           sudo locale-gen en_AU.UTF-8
-          echo "NVM_DIR=$HOME/.nvm" >> $GITHUB_ENV
+          #echo "NVM_DIR=$HOME/.nvm" >> $GITHUB_ENV
+          # Install nvm v0.39.7 (Temporary workaround for https://github.com/moodlehq/moodle-plugin-ci/issues/309).
+          curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.7/install.sh | bash
 
       - name: Install moodle-plugin-ci
         run: |