Use staging backend for cypress tests if PR base branch is staging

.github/workflows/cypress.yaml

@@ -22,11 +22,16 @@ jobs:
       - name: Checkout 📥
         uses: actions/checkout@v3
 
+      - name: Set backend branch
+        id: backend-branch
+        run: echo "::set-output name=branch::$(if [[ '${{ github.event.pull_request.base.ref }}' == 'staging' ]]; then echo 'staging'; else echo 'develop'; fi)"
+
       - name: Checkout care 📥
         uses: actions/checkout@v3
         with:
           repository: coronasafe/care
           path: care
+          ref: ${{ steps.backend-branch.outputs.branch }}
 
       - name: Start care docker containers 🐳
         run: |