Add GitHub Actions workflow

.github/workflows/back-end.yml

@@ -0,0 +1,46 @@
+# yaml-language-server: $schema=https://json.schemastore.org/github-workflow
+
+name: Integrate
+
+on:
+    pull_request: null
+    push:
+        branches:
+            - master
+
+jobs:
+    unit_tests:
+        name: Unit tests
+        strategy:
+            fail-fast: false
+            matrix:
+                php-version:
+                - 7.2
+                - 7.3
+                - 7.4
+                - 8.0
+                - 8.1
+                - 8.2
+                - 8.3
+        runs-on: ubuntu-latest
+        steps:
+        -
+            name: Set up PHP
+            uses: shivammathur/setup-php@v2
+            with:
+                php-version: ${{ matrix.php-version }}
+        -
+            name: Setup problem matcher for PHPUnit
+            run: |
+                echo ::add-matcher::${{ runner.tool_cache }}/phpunit.json
+        -
+            name: Checkout repository
+            uses: actions/checkout@v4
+        -
+            name: Install dependencies
+            uses: ramsey/composer-install@v3
+            with:
+                dependency-versions: highest
+        -
+            name: Execute unit tests
+            run: composer exec -- phpunit