Update the CI setup

- add a job for PHP 8.3
- update actions to their latest versions
- use symfony/flex to force a Symfony version instead of installing the
  fullstack package.

Author: stof

.github/workflows/ci.yaml

@@ -6,6 +6,7 @@ on:
         branches:
             - master
             - 2.x
+            - 3.x
 
 jobs:
     run:
@@ -18,6 +19,7 @@ jobs:
                     - '8.0'
                     - '8.1'
                     - '8.2'
+                    - '8.3'
                 symfony-versions: [false]
                 include:
                     -   description: 'Symfony 4.*'
@@ -26,26 +28,34 @@ jobs:
                     -   description: 'Symfony 5.*'
                         php: '8.1'
                         symfony-versions: '^5.4'
+                    -   description: 'Symfony 6.*'
+                        php: '8.2'
+                        symfony-versions: '^6.4'
         name: PHP ${{ matrix.php }} ${{ matrix.description }}
         steps:
             - name: Checkout
-              uses: actions/checkout@v3
+              uses: actions/checkout@v4
 
-            - uses: actions/cache@v3
+            - uses: actions/cache@v4
               with:
                   path: ~/.composer/cache/files
-                  key: ${{ matrix.php }}-${{ matrix.symfony-versions }}
+                  key: composer-${{ matrix.php }}-${{ matrix.symfony-versions }}-${{ hashFiles('composer.json') }}
+                  restore-keys: |
+                    composer-${{ matrix.php }}-
+                    composer-
 
             - name: Setup PHP
               uses: shivammathur/setup-php@v2
               with:
                   php-version: ${{ matrix.php }}
 
-            - name: Install dependencies
-              run: composer require "symfony/symfony:${{ matrix.symfony-versions }}" --no-update
+            - name: Install symfony/flex
+              run: composer config --global --no-plugins allow-plugins.symfony/flex true && composer global require symfony/flex
               if: matrix.symfony-versions
 
             - name: Install dependencies
+              env:
+                SYMFONY_REQUIRE: ${{ matrix.symfony-version }}
               run: composer install
 
             - name: Install PHPUnit