Feature/flatbuffers

[jamals86]

This pull request introduces several dependency updates and refactors SQL forwarding logic for cluster mode, with improvements to error handling and forwarding via gRPC. It also enhances authentication error responses to comply with security best practices.

Dependency updates:

• Updated versions for several dependencies in Cargo.toml, including uuid, clap, sysinfo, indicatif, futures-util, flatbuffers, cc, and syn, ensuring compatibility and access to latest features and bug fixes. [1] [2] [3] [4]

Cluster SQL forwarding refactor:

• Refactored SQL forwarding logic in backend/crates/kalamdb-api/src/handlers/sql/forward.rs to use gRPC for forwarding to leader and shard nodes, improving reliability and performance. Added helper functions for header extraction and node resolution, and removed legacy HTTP-based forwarding.
• Enhanced handling of NOT_LEADER errors by forwarding to the correct shard leader using gRPC, with improved error detection and fallback mechanisms.

Authentication error handling:

• Changed malformed authorization token responses to return HTTP 401 Unauthorized instead of 400 Bad Request, following OWASP guidance to avoid information disclosure. Updated related tests for this behavior. [1] [2]

SQL parsing improvements:

• Simplified the parse_execute_statement function in backend/crates/kalamdb-api/src/handlers/sql/execute.rs by delegating parsing to the canonical parser in kalamdb_sql::execute_as, reducing code duplication and improving maintainability.

Miscellaneous:

• Added a note in Notes.md regarding the need to shorten subscription IDs for better usability and future-proofing.