Initial commit: fastapi-traffic rate limiting library

- Core rate limiting with multiple algorithms (sliding window, token bucket, etc.)
- SQLite and memory backends
- Decorator and dependency injection patterns
- Middleware support
- Example usage files

fastapi_traffic/exceptions.py

@@ -0,0 +1,50 @@
+"""Custom exceptions for FastAPI Traffic rate limiter."""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from fastapi_traffic.core.models import RateLimitInfo
+
+
+class FastAPITrafficError(Exception):
+    """Base exception for all FastAPI Traffic errors."""
+
+    pass
+
+
+class RateLimitExceeded(FastAPITrafficError):
+    """Raised when a rate limit has been exceeded."""
+
+    def __init__(
+        self,
+        message: str = "Rate limit exceeded",
+        *,
+        retry_after: float | None = None,
+        limit_info: RateLimitInfo | None = None,
+    ) -> None:
+        super().__init__(message)
+        self.message = message
+        self.retry_after = retry_after
+        self.limit_info = limit_info
+
+
+class BackendError(FastAPITrafficError):
+    """Raised when a backend operation fails."""
+
+    def __init__(
+        self,
+        message: str = "Backend operation failed",
+        *,
+        original_error: Exception | None = None,
+    ) -> None:
+        super().__init__(message)
+        self.message = message
+        self.original_error = original_error
+
+
+class ConfigurationError(FastAPITrafficError):
+    """Raised when there is a configuration error."""
+
+    pass