ci/cd: add explicit permissions to actions

.github/workflows/unit-tests.yml

@@ -11,13 +11,16 @@ on:
 
 jobs:
   test-backend:
+    permissions:
+      contents: read
+      actions: write
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
       - uses: actions/setup-go@v5
         with:
-          go-version-file: 'backend/go.mod'
-          cache-dependency-path: 'backend/go.sum'
+          go-version-file: "backend/go.mod"
+          cache-dependency-path: "backend/go.sum"
       - name: Install dependencies
         working-directory: backend
         run: |