Fix #7060: Return 400 InvalidRequest instead of 500 for context canceled errors (#7309)

When a client cancels an HTTP request (e.g., connection timeout, client
disconnect), the context gets canceled and propagates through the system
as "context canceled" or "code = Canceled" errors. These errors were
being treated as internal server errors (500) when they should be treated
as client errors (400).

Problem:
- Client cancels request or connection times out
- Filer fails to assign file ID with "context canceled"
- S3 API returns HTTP 500 Internal Server Error
- This is incorrect - it's a client issue, not a server issue

Solution:
Added detection for context canceled errors in filerErrorToS3Error():
- Detects "context canceled" and "code = Canceled" in error strings
- Returns ErrInvalidRequest (HTTP 400) instead of ErrInternalError (500)
- Properly attributes the error to the client, not the server

Changes:
- Updated filerErrorToS3Error() to detect context cancellation
- Added test cases for both gRPC and simple context canceled errors
- Maintains existing error handling for other error types

This ensures:
- Clients get appropriate 4xx error codes for their canceled requests
- Server metrics correctly reflect that these are client issues
- Monitoring/alerting won't trigger false positives for client timeouts

Fixes #7060

0 files changed, 0 insertions, 0 deletions