[5.x] Add a config for specifying the default layout

config/system.php

@@ -194,4 +194,15 @@
 
     'fake_sql_queries' => config('app.debug'),
 
+    /*
+    |--------------------------------------------------------------------------
+    | Layout
+    |--------------------------------------------------------------------------
+    |
+    | Define the default layout that will be used by views.
+    |
+    */
+
+    'layout' => env('STATAMIC_LAYOUT', 'layout'),
+
 ];

src/Entries/Collection.php

@@ -442,7 +442,7 @@ public function layout($layout = null)
         return $this
             ->fluentlyGetOrSet('layout')
             ->getter(function ($layout) {
-                return $layout ?? 'layout';
+                return $layout ?? config('statamic.system.layout', 'layout');
             })
             ->args(func_get_args());
     }

src/Http/Controllers/FrontendController.php

@@ -45,7 +45,7 @@ public function route(Request $request, ...$args)
 
         $view = app(View::class)
             ->template($view)
-            ->layout(Arr::get($data, 'layout', 'layout'))
+            ->layout(Arr::get($data, 'layout', config('statamic.system.layout', 'layout')))
             ->with($data)
             ->cascadeContent($this->getLoadedRouteItem($data));
 

src/Taxonomies/Taxonomy.php

@@ -436,7 +436,7 @@ public function layout($layout = null)
         return $this
             ->fluentlyGetOrSet('layout')
             ->getter(function ($layout) {
-                return $layout ?? 'layout';
+                return $layout ?? config('statamic.system.layout', 'layout');
             })
             ->args(func_get_args());
     }

tests/Routing/RoutesTest.php

@@ -341,4 +341,16 @@ public function it_loads_term_by_binding()
         $this->get('/bindings/term/title/Blog2')
             ->assertNotFound();
     }
+
+    #[Test]
+    public function it_uses_a_non_default_layout()
+    {
+        config()->set('statamic.system.layout', 'custom-layout');
+        $this->viewShouldReturnRaw('custom-layout', 'Custom layout {{ template_content }}');
+        $this->viewShouldReturnRaw('test', 'Hello {{ hello }}');
+
+        $this->get('/basic-route-with-data')
+            ->assertOk()
+            ->assertSee('Custom layout');
+    }
 }