[Breaking Change] v4.0.0 / v4.0.1 introduces Express 5 (SemVer Violation)

[Sandbye]

We recently encountered a production regression where our Google Cloud Functions (HTTP) stopped processing req.query correctly after a minor/patch update.

Upon investigation, we discovered that functions-framework was updated (via ^4.0.0) to a version that internally bumps Express from v4 to v5.

This is a Major Breaking Change. Express 5 introduces significant changes to the request object and query parsing behavior (removing legacy parser support) which breaks existing function signatures that rely on Express 4 behavior.

The Issue

Previous Version: 4.0.0 (Works perfectly, Express 4 behavior).

Current Version: 4.0.1 (Breaks req.query, req.params, Express 5 behavior).

In our specific case, req.query is now undefined or incorrectly parsed for GET requests, causing valid traffic to fail.

Related PR Comment:
#715 (comment)