Description

This PR implements the AchievementsController to expose a new endpoint:

• GET /users/:id/achievements: Returns the list of achievements unlocked by a user, including the achievement title, icon URL, and the timestamp when it was unlocked.

Changes

• Created AchievementsController under users/controllers/
• Injected AchievementsService to fetch achievements
• Endpoint returns structured achievement data
• Added unit tests for AchievementsService.findByUserId
• Ensured proper typing and filtering of output

Example Response:

[
  {
    "id": "1",
    "title": "First Achievement",
    "iconUrl": "https://cdn.app/icons/first.svg",
    "unlockedAt": "2024-07-26T12:00:00.000Z"
  },
]
Ccloses issue #96