feat: Add rate limiting middleware with SlowAPI

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/middleware/rate_limit_decorators.py

@@ -0,0 +1,72 @@
+#!/usr/bin/env python3
+
+"""
+Rate limiting decorators for DocuElevate API endpoints.
+
+This module provides convenient decorators to apply rate limits to specific endpoints.
+Import the limiter from main.py state and use these decorators to protect endpoints.
+"""
+
+from functools import wraps
+
+from fastapi import Request
+
+# Import will happen at runtime to avoid circular dependencies
+_limiter = None
+
+
+def get_limiter():
+    """Get the limiter instance from the app state."""
+    global _limiter
+    if _limiter is None:
+        from app.main import app
+
+        _limiter = app.state.limiter
+    return _limiter
+
+
+def limit(rate_limit: str):
+    """
+    Apply a rate limit to an endpoint.
+    
+    Args:
+        rate_limit: Rate limit string (e.g., "10/minute", "100/hour")
+        
+    Returns:
+        Decorator function
+        
+    Example:
+        @router.post("/login")
+        @limit("10/minute")
+        async def login(request: Request):
+            ...
+    """
+
+    def decorator(func):
+        limiter = get_limiter()
+        # Apply the slowapi limit decorator
+        return limiter.limit(rate_limit)(func)
+
+    return decorator
+
+
+def exempt():
+    """
+    Exempt an endpoint from rate limiting.
+    
+    Returns:
+        Decorator function
+        
+    Example:
+        @router.get("/health")
+        @exempt()
+        def health_check():
+            ...
+    """
+
+    def decorator(func):
+        limiter = get_limiter()
+        # Apply the slowapi exempt decorator
+        return limiter.exempt(func)
+
+    return decorator