[FEATURE] Implement login and register APIs

[SeungjaeLim]

Description

Create login and register API endpoints to handle user authentication and registration.

Motivation

User authentication and registration are essential features for managing access to the application and securing user data.

Proposed Solution

• Design the API endpoints for user registration and authentication (e.g., /api/register and /api/login).
• Implement the register API to:
  • Validate user input (ID, password, and additional information).
  • Store the new user in the MongoDB database.
  • Return a success message or appropriate error response.
• Implement the login API to:
  • Validate user input (ID and password).
  • Authenticate the user against the stored data in MongoDB.
  • Return a success message with a session token or appropriate error response.

Additional Context

N/A