✨ (auth): Añade permisos tipados

Sustituye las claves de permiso `&str` sueltas por el trait `Permission`
(clave, etiqueta y grupo), y añade `require_permission()` para cortar un
handler con `ErrorPage::AccessDenied` antes de construir nada.

Para que `require_permission()` pueda fallar sin un `Context` previo,
`ErrorPage` pasa a envolver `Option<HttpRequest>`, `Context::new()`
recibe ahora `HttpRequest` sin `Option`, y se añade `Context::admin()`
para la plantilla de administración.

tests/auth.rs

@@ -39,7 +39,7 @@ async fn current_user_propagates_from_request_extensions() {
             display_name: "Bob".to_owned(),
         })
         .to_http_request();
-    let cx = Context::new(Some(req));
+    let cx = Context::new(req);
     let user = cx.current_user();
     assert!(user.is_authenticated());
     assert_eq!(user.id(), Some(7));

tests/component_html.rs

@@ -50,7 +50,7 @@ async fn component_html_can_access_request_path() {
     let req = web::test::TestRequest::get()
         .uri("/hello/world")
         .to_http_request();
-    let mut cx = Context::new(Some(req));
+    let mut cx = Context::new(req);
 
     let mut component = Html::with(|cx| {
         let path = cx

tests/component_template.rs

@@ -46,10 +46,10 @@ impl Theme for MarkerTheme {
 
 #[pagetop::test]
 async fn default_template_identity_is_independent_of_theme() {
-    let cx = Context::new(None);
+    let cx = Context::default();
     assert_eq!(cx.template().name(), "standard");
 
-    let cx = Context::new(None).with_theme(&MarkerTheme);
+    let cx = Context::default().with_theme(&MarkerTheme);
     assert_eq!(cx.template().name(), "standard");
 }
 
@@ -67,7 +67,7 @@ async fn admin_template_identity_is_independent_of_theme() {
 async fn explicit_template_is_not_overridden_by_a_later_with_theme() {
     // A template explicitly set with `with_template()` prevails even if `with_theme()` is called
     // afterwards.
-    let cx = Context::new(None)
+    let cx = Context::default()
         .with_template(&CoreTemplate::Admin)
         .with_theme(&pagetop::base::theme::Basic);
 

tests/route.rs

@@ -3,7 +3,7 @@ use pagetop::prelude::*;
 // Forces an effective language different from the default negotiated one (en-US, with no `?lang` in
 // the request), so that `Context::route()` decides to propagate `?lang=...` in local routes.
 fn cx_with_lang(lang: &str) -> Context {
-    Context::new(None).with_langid(&Locale::resolve(lang))
+    Context::default().with_langid(&Locale::resolve(lang))
 }
 
 // **< Route - automatic detection of external URLs >***********************************************
@@ -107,7 +107,7 @@ async fn route_with_captures_dynamic_values_from_the_environment() {
 
 #[pagetop::test]
 async fn route_default_resolves_to_an_empty_path() {
-    let cx = Context::new(None);
+    let cx = Context::default();
     assert_eq!(Route::default().resolve(&cx).to_string(), "");
 }