refactor: use english for routes, parameters and internal messages

tests/Security/EpClientTest.php

@@ -56,7 +56,7 @@ class EpClientTest extends KernelTestCase
         $request->getSession()->set('oauth2state', 'abc');
 
         $this->expectException(AuthorizationRequestException::class);
-        $this->expectExceptionMessage('keinen Code');
+        $this->expectExceptionMessage('no authorization code');
 
         $this->client()->fetchAccessToken($request);
     }
@@ -71,7 +71,7 @@ class EpClientTest extends KernelTestCase
         $request->getSession()->set('oauth2state', 'expected');
 
         $this->expectException(AuthorizationRequestException::class);
-        $this->expectExceptionMessage('state-Parameter');
+        $this->expectExceptionMessage('state parameter does not match');
 
         $this->client()->fetchAccessToken($request);
     }