public URI baseUri() {
    return server.configuration().baseUri();
  }
@Test
  void run_callback() {
    var baseUri = application.baseUri();

    var sessionID = UUID.randomUUID().toString();

    var response =
        given()
            .log()
            .all()
            .cookie("session_id", sessionID)
            .formParam("code", "code")
            .when()
            .get(baseUri.resolve(CALLBACK_PATH))
            .then()
            .contentType(ContentType.HTML)
            .statusCode(400)
            .extract()
            .response();

    var responseBody = response.getBody().asString();
    assertTrue(responseBody.contains("de-DE"));
    assertTrue(
        responseBody.contains(
            "Oops, Sitzung unbekannt oder abgelaufen. Bitte starten Sie erneut."));
  }