feat: integrate Kakao OAuth for user authentication and enhance user repository

- Added Kakao OAuth client implementation for handling authentication flows.
- Updated user repository to support OAuth-based user creation and retrieval.
- Introduced Redis-based session management for OAuth sessions.
- Enhanced in-memory user repository to handle OAuth user data.
- Updated environment configuration files to include new OAuth settings.
- Modified API routes to support Kakao login and registration flows.
- Added Prisma schema updates for user model to accommodate OAuth fields.
- Implemented tests for the new authentication flow and user repository methods.

app/gateway-api/src/index.ts

@@ -15,6 +15,9 @@ export * from './auth/inMemorySessionService.js';
 export * from './auth/redisSessionService.js';
 export * from './auth/redisKeys.js';
 export * from './auth/flushPublisher.js';
+export * from './auth/kakaoClient.js';
+export * from './auth/oauthSessionStore.js';
+export * from './auth/postgresUserRepository.js';
 
 const isMain = (): boolean => {
     if (!process.argv[1]) {