Add authenticated download URLs for headless frontends (#995)

* feat: add authenticated download URLs for headless frontends

- Add downloadNonce and downloadUrl fields to DownloadableItem type
  using the existing Protected Router session transfer pattern
- Add preAuthDownloadUrl field (toggleable via settings) that generates
  tokenized download URLs for direct file access without cookie auth
- Add download_url nonce handling to Protected_Router
- Add enable_pre_auth_download_urls and download_url_nonce_param settings
- Add GraphQLE2E helpers for checkout and account shortcode pages
- Rewrite ProtectedRouterCest to test redirect flow without JS-dependent
  page content assertions, add account and payment method URL tests
- Add DownloadableItemAuthCest with 5 e2e tests covering both options

* fix: test suite stability and code coverage collection

- Add WC_Unit_Tests_Bootstrap stub to wpunit bootstrap to bypass
  wc_get_product_visibility_term_ids static cache between suites
- Add setWooGraphQLSetting helper to GraphQLE2E for safe individual
  field updates to woographql_settings option with proper defaults
- Update all functional tests to use setWooGraphQLSetting instead of
  replacing the entire woographql_settings option
- Fix createRelated factory to use explicit shared category instead
  of relying on default Uncategorized category
- Add download_url to ProtectedRouterTest nonce names assertion
- Remove debug logs from ProductQueriesTest and ProductsQueriesTest
- Fix CI workflow to run suites separately and aggregate coverage
  via phpcov merge
- Wire c3.php into WordPress index.php for remote coverage collection
- Update .coveralls.yml service_name to github-actions
- Clean up Xdebug 2 settings in Dockerfile

* chore: Linter compliances met

* fix: ensure tests/_output is writable for c3.php coverage collection

* devops: .env.docker removed from setup

* devops: split CI into separate jobs per suite with retry and coverage aggregation

* devops: add +Coverage indicator to CI job names

* devops: add --fail-fast to first run, fix retry to mark job as passing on retry success

bin/entrypoint.sh

@@ -31,8 +31,6 @@ fi
 # Update our domain to just be the docker container's IP address
 export WORDPRESS_DOMAIN=${WORDPRESS_DOMAIN-$( hostname -i )}
 export WORDPRESS_URL="http://$WORDPRESS_DOMAIN"
-echo "WORDPRESS_DOMAIN=$WORDPRESS_DOMAIN" > "$PROJECT_DIR/.env.docker"
-echo "WORDPRESS_URL=$WORDPRESS_URL" >> "$PROJECT_DIR/.env.docker"
 
 # Config WordPress
 if [ -f "${WP_ROOT_FOLDER}/wp-config.php" ]; then
@@ -145,6 +143,16 @@ if [ ! -d "wp-content/uploads" ]; then
 fi
 chmod 777 -R wp-content/uploads
 
+# Download c3 for testing.
+if [ ! -f "$PROJECT_DIR/c3.php" ]; then
+    echo "Downloading Codeception's c3.php"
+    curl -L 'https://raw.github.com/Codeception/c3/2.0/c3.php' > "$PROJECT_DIR/c3.php"
+fi
+
+# Ensure test output directory is writable by Apache for c3.php coverage collection.
+mkdir -p "$PROJECT_DIR/tests/_output"
+chmod 777 -R "$PROJECT_DIR/tests/_output"
+
 if [ -n "$RUNNING_TEST_STANDALONE" ]; then
 	service apache2 start
 fi