feature: improve error handling

[tyrchen]

No description provided.

[Copilot]

Pull Request Overview

This PR focuses on improving error handling across the PostgreSQL MCP codebase. Key changes include adding detailed error variants with PgMcpError in src/pg.rs, updating error mappings in src/mcp.rs to use a dedicated helper (map_pg_error), and adding additional test scenarios for error cases in tests/mcp_test.rs.

Reviewed Changes

Copilot reviewed 16 out of 16 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/mcp_test.rs	Added error scenario tests to verify improved error messaging and SQL validation failures
src/pg.rs	Introduced explicit PgMcpError variants and refined SQL validation logic
src/mcp.rs	Refactored error mapping to use a dedicated helper function for consistent error conversion
src/main.rs	Simplified SSE server startup using serve_with_config
Cargo.toml & documentation	Updated dependency versions and adjusted documentation to reflect improved error handling

Comments suppressed due to low confidence (2)

tests/mcp_test.rs:389

• Using a hard-coded error code substring ('-32603') in your assertions might be brittle if error messages change in the future. Consider checking against structured error variants or error types.

err.to_string().contains("Mcp error: -32603: Connection not found") // Match actual stdio transport error

src/pg.rs:49

• [nitpick] In the conversion from sqlx::Error to PgMcpError, consider capturing more specific context (e.g. the operation context) instead of defaulting to 'unknown'. This can improve debugging clarity when database errors occur.

if let Some(db_err) = e.as_database_error() {