Detect recursion in scheme extension

[giuscris]

This pull request improves the scheme extension mechanism in the Scheme class by adding recursion protection and allowing schemes to be extended by ID as well as by instance. The main changes focus on preventing infinite loops when schemes extend each other, directly or indirectly, and improving error handling.

Scheme extension improvements:

• Added a static property self::$extending to track currently extending scheme IDs and detect recursion during extension, throwing a new RecursionException if a recursive extension is detected. [1] [2]
• Updated the extend method to accept either a Scheme instance or a scheme ID (string), improving flexibility when extending schemes.
• Modified the constructor to pass the scheme ID instead of the instance to the extend method, aligning with the new method signature.
• Improved exception handling by throwing RecursionException when recursion is detected and updating docblocks to reflect new exception types. [1] [2]
• Added the import for the new RecursionException class.

[Copilot]

Pull request overview

This PR hardens the Formwork\Schemes\Scheme extension mechanism by preventing recursive extension chains and by allowing extension to be triggered using either a Scheme instance or a scheme ID string.

Changes:

• Added recursion protection for scheme extension via a static in-progress ID tracker and a new RecursionException.
• Updated Scheme::extend() to accept Scheme|string and adjusted the constructor to pass the configured extend ID directly.
• Updated docblocks/imports to reflect the new exception and signature changes.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.