Show warning in case the server cuts out auth header

appinfo/routes.php

@@ -33,6 +33,7 @@
 		# Routes for admin settings
 		['name' => 'settings#addClient', 'url' => '/clients', 'verb' => 'POST'],
 		['name' => 'settings#deleteClient', 'url' => '/clients/{id}/delete', 'verb' => 'POST'],
+		['name' => 'settings#test', 'url' => '/test', 'verb' => 'POST'],
 		# Routes for personal settings
 		['name' => 'settings#revokeAuthorization', 'url' => '/clients/{id}/revoke', 'verb' => 'POST']
 	]

js/settings.js

@@ -27,4 +27,19 @@ $(document).ready(function () {
 			}
 		}, false);
 	}
+
+	var testToken = Math.random().toString();
+	$.ajax({
+		type: 'POST',
+		url: OC.generateUrl('apps/oauth2/test'),
+		headers: {
+			'Authorization': 'Bearer ' + testToken
+		}
+	}).done(function(data){
+		if (data.authHeaderFound !== true) {
+			OC.Notification.show(
+				'Oauth2 will not work properly as your webserver does not pass Authorization header to PHP.'
+			);
+		}
+	});
 });

lib/Controller/SettingsController.php

@@ -27,6 +27,7 @@
 use OCA\OAuth2\Utilities;
 use OCP\AppFramework\Controller;
 use OCP\AppFramework\Db\DoesNotExistException;
+use OCP\AppFramework\Http\DataResponse;
 use OCP\AppFramework\Http\JSONResponse;
 use OCP\AppFramework\Http\RedirectResponse;
 use OCP\IL10N;
@@ -218,4 +219,15 @@ private function sendErrorResponse($message) {
 			]
 		);
 	}
+
+	/**
+	 * Checks if the server configured properly
+	 *
+	 * @return string[]
+	 */
+	public function test() {
+		return [
+			'authHeaderFound' => $this->request->getHeader('Authorization') !== null
+		];
+	}
 }

tests/Unit/Controller/SettingsControllerTest.php

@@ -41,7 +41,7 @@ class SettingsControllerTest extends TestCase {
 	/** @var string $name */
 	private $appName;
 
-	/** @var IRequest */
+	/** @var IRequest | \PHPUnit\Framework\MockObject\MockObject */
 	private $request;
 
 	/** @var SettingsController $controller */
@@ -257,4 +257,22 @@ public function testRevokeAuthorization() {
 		$this->assertEquals(0, \count($this->accessTokenMapper->findAll()));
 		$this->assertEquals(0, \count($this->refreshTokenMapper->findAll()));
 	}
+
+	public function healthDataProvider() {
+		return [
+			['someToken', ['authHeaderFound' => true]],
+			[null, ['authHeaderFound' => false]]
+		];
+	}
+
+	/**
+	 * @dataProvider healthDataProvider
+	 * @param string $authHeader
+	 * @param array $expectedResult
+	 */
+	public function testTest($authHeader, $expectedResult) {
+		$this->request->method('getHeader')->willReturn($authHeader);
+		$result = $this->controller->test();
+		$this->assertEquals($result, $expectedResult);
+	}
 }