Function cookie_name 

pub fn cookie_name() -> String

This app’s own session cookie name, derived from Config::app_name - public so larust_testing::TestClient::acting_as can adopt a session by hand-crafting the exact same Cookie header the router’s own session layer (above) would issue, without needing a real /login round trip. Must stay the single source of truth for the name: any second place that re-derives it independently risks drifting out of sync with whatever session_layer actually configured.

Uses larust_core::try_config(), not config() - a handful of narrow router-building test helpers (see e.g. examples/blog/tests/store_post_test.rs) build a session-bearing router directly off a bare pool, with no Application::new() call anywhere in the test at all, since nothing else they exercise needs one. Falling back to a fixed name in that case (rather than panicking) keeps this a purely additive change - every real app (main.rs always calls Application::new() first) still gets a properly app-scoped cookie name; a test with no Application just gets a stable shared one instead, which is harmless since nothing about in-process oneshot()- driven tests risks the actual cross-app cookie collision this scoping exists to prevent in a real browser.