# Plan: UserId Value Object

## Status: COMPLETED

## Objective
Create a UserId value object in the marketplace domain with an immutable UUID value.

## Decisions Made
- **Location**: `domain/marketplace/user_id.py`
- **Class style**: `@dataclass(frozen=True)` for immutability
- **Tests**: Yes

## Value Object Structure
```python
@dataclass(frozen=True)
class UserId:
    value: UUID
```

## Files Created
- `domain/marketplace/user_id.py`
- `tests/test_user_id.py`

## Test Results
- `test_user_id_creation` - PASSED
- `test_user_id_is_immutable` - PASSED
- `test_user_id_equality` - PASSED