feat: add query_log_stdout config for pgcat-style query logging

[marcomicera]

Summary

Adds a query_log_stdout general config option that logs every query to stdout in pgcat-style format: [pool: db][user: user] query.

• Configurable via pgdog.toml or PGDOG_QUERY_LOG_STDOUT
• Defaults to false
• Logs at the start of query parsing so queries are captured even when the parser is bypassed

Test plan

• Run pgdog with query_log_stdout = true and confirm queries appear in logs

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[codecov]

Codecov Report

❌ Patch coverage is 66.66667% with 6 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pgdog/src/frontend/router/parser/query/mod.rs	25.00%	6 Missing ⚠️

📢 Thoughts on this report? Let us know!

[marcomicera]

Adding tests to cover these 6 missing lines... 👨‍💻

[levkk]

I would put the db/user at the end to match our existing log format. Not sure if it's right, but at least it's consistent.

SELECT * FROM users WHERE id = $1 [database: oranges, user: apples]

[levkk]

I would put this somewhere at the top of QueryEngine::handle, in its own function. The parser is not guaranteed to be used if, for example, query_parser = "off" in the config.

The query will be available as:

if context.query_log_stdout {
  if let Ok(Some(query)) = context.client_request.query() {
      info!("{} [database: {}, user: {}]", query.query(), ...);
   }
}

Also, try to follow the same pattern as other settings, e.g. load them at request start only here:

pgdog/pgdog/src/frontend/client/mod.rs

Line 573 in beabd7d

let config = config::config();

Loading the config (ArcSwap + Arc clone) is effectively free, but not entirely, so we try to do it once per query at most.