Lumen: Exception handling breaks HTTP response

[francescobianco]

Labels: bug, lumen, error-handling
Context: Lumen 9.x (lightweight Laravel variant)

Description:
Unhandled exceptions from Openapi SDK are returned as HTML 500 pages instead of JSON. The SDK throws \Exception instead of domain-specific exceptions.

Expected:
Use structured exceptions implementing Throwable and compatible with Lumen’s JSON error formatter.

Impact:
API Gateway responses become inconsistent for frontend clients.