Complete Task 1.3 - Authentication System Implementation

✅ Implemented comprehensive authentication system:
- Abstract AuthHandler base class with pluggable architecture
- APIKeyAuth for API key authentication (string auto-conversion)
- JWTAuth for JWT token authentication with expiration handling
- NoAuth for testing and public instances
- Full integration with WikiJSClient for automatic header management

🔧 Fixed packaging issues:
- Updated pyproject.toml with required project metadata fields
- Fixed utility function exports in utils/__init__.py
- Package now installs correctly in virtual environments

🧪 Validated with comprehensive tests:
- All authentication methods working correctly
- Proper error handling for invalid credentials
- Type validation and security features

📊 Progress: Phase 1 MVP Development now 60% complete
🎯 Next: Task 1.4 - Pages API implementation

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

wikijs/auth/base.py

@@ -0,0 +1,97 @@
+"""Base authentication interface for wikijs-python-sdk.
+
+This module defines the abstract base class for all authentication handlers,
+providing a consistent interface for different authentication methods.
+"""
+
+from abc import ABC, abstractmethod
+from typing import Dict, Optional
+
+
+class AuthHandler(ABC):
+    """Abstract base class for Wiki.js authentication handlers.
+    
+    This class defines the interface that all authentication implementations
+    must follow, ensuring consistent behavior across different auth methods.
+    """
+
+    @abstractmethod
+    def get_headers(self) -> Dict[str, str]:
+        """Get authentication headers for HTTP requests.
+        
+        Returns:
+            Dict[str, str]: Dictionary of headers to include in requests.
+            
+        Raises:
+            AuthenticationError: If authentication is invalid or expired.
+        """
+        pass
+
+    @abstractmethod
+    def is_valid(self) -> bool:
+        """Check if the current authentication is valid.
+        
+        Returns:
+            bool: True if authentication is valid, False otherwise.
+        """
+        pass
+
+    @abstractmethod
+    def refresh(self) -> None:
+        """Refresh the authentication if possible.
+        
+        For token-based authentication, this should refresh the token.
+        For API key authentication, this is typically a no-op.
+        
+        Raises:
+            AuthenticationError: If refresh fails.
+        """
+        pass
+
+    def validate_credentials(self) -> None:
+        """Validate credentials and refresh if necessary.
+        
+        This is a convenience method that checks validity and refreshes
+        if needed. Subclasses can override for custom behavior.
+        
+        Raises:
+            AuthenticationError: If credentials are invalid or refresh fails.
+        """
+        if not self.is_valid():
+            self.refresh()
+        
+        if not self.is_valid():
+            from ..exceptions import AuthenticationError
+            raise AuthenticationError("Authentication credentials are invalid")
+
+
+class NoAuth(AuthHandler):
+    """No-authentication handler for testing or public instances.
+    
+    This handler provides an empty authentication implementation,
+    useful for testing or when accessing public Wiki.js instances
+    that don't require authentication.
+    """
+
+    def get_headers(self) -> Dict[str, str]:
+        """Return empty headers dict.
+        
+        Returns:
+            Dict[str, str]: Empty dictionary.
+        """
+        return {}
+
+    def is_valid(self) -> bool:
+        """Always return True for no-auth.
+        
+        Returns:
+            bool: Always True.
+        """
+        return True
+
+    def refresh(self) -> None:
+        """No-op for no-auth.
+        
+        This method does nothing since there's no authentication to refresh.
+        """
+        pass