test: 로그인 관련 테스트시 쿠키를 얻을 수 있는 공용 메서드 추가

backend/src/test/java/com/funeat/acceptance/common/LoginSteps.java

@@ -0,0 +1,21 @@
+package com.funeat.acceptance.common;
+
+import io.restassured.RestAssured;
+import io.restassured.http.Cookies;
+import io.restassured.response.ExtractableResponse;
+import io.restassured.response.Response;
+
+@SuppressWarnings("NonAsciiCharacters")
+public class LoginSteps {
+
+    public static Cookies 로그인_쿠키를_얻는다() {
+        final ExtractableResponse<Response> response = RestAssured.given()
+                .queryParam("code", "test")
+                .when()
+                .get("/login/oauth2/code/kakao")
+                .then()
+                .extract();
+
+        return response.detailedCookies();
+    }
+}