add unittests for php 8.1 - 8.3

.forgejo/workflows/phpunit.yml

@@ -19,7 +19,7 @@ jobs:
           MYSQL_ROOT_PASSWORD: root
     strategy:
       matrix:
-        php-versions: ['8.1']
+        php-versions: ['8.1', '8.2', '8.3']
     name: Run phpunit tests
     env:
       extensions: mysql
@@ -42,7 +42,7 @@ jobs:
         uses: https://code.forgejo.org/actions/cache@v4
         with:
           path: |
-            ./vendor/
+            ./vendor/install
           key: cache-composer-phpunit-1
 
       - name: Setup PHP
@@ -54,9 +54,8 @@ jobs:
         env:
           runner: self-hosted
 
-      - name: Install PHP Unit
+      - name: Install PHPUnit and PHPUnit-Polyfills
         if: steps.cache-composer-phpunit.outputs.cache-hit != 'true'
-        # Polyfills requires all needed packages including phpunit itself.
         run: composer require --dev yoast/phpunit-polyfills:"^3.0"
 
       - name: Install and cache mysqladmin needed to initialize the test database