Centralize Vary header declaration in ActivityPub::isRequest

- Vary header should be set every time we vary the display based on an HTTP header value

src/App.php

@@ -695,6 +695,9 @@ class App
 				$module = $router->getModule();
 			}
 
+			// Display can change depending on the requested language, so it shouldn't be cached whole
+			header('Vary: Accept-Language', false);
+
 			// Processes data from GET requests
 			$httpinput = $httpInput->process();
 			$input     = array_merge($httpinput['variables'], $httpinput['files'], $request ?? $_REQUEST);

src/Module/ActivityPub/Objects.php

@@ -46,8 +46,6 @@ class Objects extends BaseModule
 			throw new HTTPException\BadRequestException();
 		}
 
-		header('Vary: Accept', false);
-
 		if (!ActivityPub::isRequest()) {
 			DI::baseUrl()->redirect(str_replace('objects/', 'display/', DI::args()->getQueryString()));
 		}

src/Module/Friendica.php

@@ -115,8 +115,6 @@ class Friendica extends BaseModule
 
 	protected function rawContent(array $request = [])
 	{
-		header('Vary: Accept', false);
-
 		// @TODO: Replace with parameter from router
 		if (DI::args()->getArgc() <= 1 || (DI::args()->getArgv()[1] !== 'json')) {
 			if (!ActivityPub::isRequest()) {

src/Module/Item/Display.php

@@ -88,8 +88,6 @@ class Display extends BaseModule
 
 	protected function content(array $request = []): string
 	{
-		header('Vary: Accept', false);
-
 		if (ActivityPub::isRequest()) {
 			$this->baseUrl->redirect(str_replace('display/', 'objects/', $this->args->getQueryString()));
 		}

src/Module/Profile/Profile.php

@@ -80,8 +80,6 @@ class Profile extends BaseProfile
 
 	protected function rawContent(array $request = [])
 	{
-		header('Vary: Accept', false);
-
 		if (ActivityPub::isRequest()) {
 			$user = $this->database->selectFirst('user', ['uid'], ['nickname' => $this->parameters['nickname'] ?? '', 'account_removed' => false]);
 			if ($user) {

src/Module/Xrd.php

@@ -38,6 +38,8 @@ class Xrd extends BaseModule
 {
 	protected function rawContent(array $request = [])
 	{
+		header('Vary: Accept', false);
+
 		// @TODO: Replace with parameter from router
 		if (DI::args()->getArgv()[0] == 'xrd') {
 			if (empty($_GET['uri'])) {

src/Protocol/ActivityPub.php

@@ -87,6 +87,8 @@ class ActivityPub
 	 */
 	public static function isRequest(): bool
 	{
+		header('Vary: Accept', false);
+
 		$isrequest = stristr($_SERVER['HTTP_ACCEPT'] ?? '', 'application/activity+json') ||
 			stristr($_SERVER['HTTP_ACCEPT'] ?? '', 'application/json') ||
 			stristr($_SERVER['HTTP_ACCEPT'] ?? '', 'application/ld+json');