Create Comprehensive Tests for Rooms App

# Create Comprehensive Tests for Rooms App

> [!IMPORTANT]
> This issue has been created before the merging of #52.
> Therefore, the outline / tests / function names / variables names below may change.

## Description

The `rooms` app currently has no test coverage (tests.py is empty). We need to implement comprehensive unit and integration tests to ensure the authentication and user management functionality works correctly.

## Scope

The following components need test coverage:

### 1. **Models** (`server/api/room/models.py`)

- `Location` model
- [ ] Test `__str__` method returns correct format
- `Amenity` model
- [ ] Test `__str__` method returns correct format
- `Room` model
- [ ] Test `__str__` method returns correct format
- [ ] ...

### 2. **Serializers** (`server/api/room/serializers.py:6`)

- `AmenitySerializer`
- [ ] ...
- `LocationSerializer`
- [ ] ...
- `RoomSerializer`
- [ ] ...

### 3. **Views** (`server/api/room/views.py:15`)

- `RoomViewSet`
- [ ] ...
- `LocationViewSet`
- [ ] ...
- `AmenityViewSet`
- [ ] ...

### 4. **URLs** (`server/api/room/urls.py`)

- [ ] Test `/rooms/` endpoint resolves correctly
- [ ] Test `/locations/` endpoint resolves correctly
- [ ] Test `/amenities/` endpoint resolves correctly
- [ ] Test URL name resolution