add test for socket (#2674)

# Add Comprehensive Tests for Socket Module

## Overview
This PR adds comprehensive test coverage for the `socket` module,
ensuring robust testing of WebSocket connection handling,
authentication, session management, and data persistence functionality.

## Changes
- **New Test File**: `backend/tests/test_socket.py` with 30 test cases
- **Test Coverage**: Authentication, session management, thread
resumption, user environment loading, and edge cases

## Test Suites

### 1. Authentication Tests (11 tests)
- **`TestGetTokenFromCookie`**: Token extraction from HTTP cookies
  - Valid cookie handling
  - Missing cookie scenarios
  - Empty cookie handling
- **`TestGetToken`**: Token retrieval wrapper functionality
- **`TestAuthenticateConnection`**: User authentication flow
  - Valid token authentication
  - Missing token handling
  - Invalid token scenarios
  - Exception handling

### 2. Session Management Tests (4 tests)
- **`TestRestoreExistingSession`**: Session restoration with new socket
IDs
  - Successful restoration
  - Session not found scenarios
- **`TestCleanSession`**: Session cleanup marking
  - Existing session cleanup
  - Non-existent session handling

### 3. Data Persistence Tests (4 tests)
- **`TestPersistUserSession`**: Session metadata persistence
  - Persistence with data layer
  - Behavior without data layer
  - Empty metadata handling

### 4. Thread Resumption Tests (8 tests)
- **`TestResumeThread`**: Thread restoration functionality
  - Missing data layer handling
  - User authorization checks
  - Thread not found scenarios
  - Successful thread resumption
  - JSON string metadata parsing
  - Empty metadata handling

### 5. User Environment Tests (6 tests)
- **`TestLoadUserEnv`**: User environment variable loading
  - Valid JSON parsing
  - Required key validation
  - Missing required keys error handling
  - Empty JSON handling
  - Bug documentation for `None` input with required keys

### 6. Edge Cases Tests (9 tests)
- **`TestSocketEdgeCases`**: Boundary conditions and error scenarios
  - `None` session ID handling
  - Empty metadata persistence
  - Empty JSON environments
  - Exception propagation

## Coverage Details
- **Total Tests**: 30
- **Async Tests**: 17 (using `pytest.mark.asyncio`)
- **Mocking Strategy**: Comprehensive use of `AsyncMock` and `Mock` for
external dependencies
- **Cross-Platform**: Compatible with Windows and Linux environments

## Key Features
- **Proper Mocking**: All external dependencies (data layer, config,
authentication) are mocked
- **Error Handling**: Tests cover both success and failure scenarios
- **Bug Documentation**: Tests document existing bugs in the codebase
(e.g., `UnboundLocalError` in `load_user_env`)
- **Session Cleanup**: Proper cleanup of `user_sessions` dictionary in
tests to avoid side effects

## Testing Approach
- Uses `unittest.mock` for patching external dependencies
- Employs `pytest-asyncio` for async function testing
- Maintains test isolation with proper setup and teardown
- Follows existing test patterns from other test files

Contribution by Gittensor, learn more at https://gittensor.io/

Author: codomposer