fix: allow custom HTTP status codes from entrypoint handlers (#284)

[aidandaly24]

fix: allow custom HTTP status codes from entrypoint handlers (#284)

Issue

Closes #284

@app.entrypoint handlers could only produce HTTP 200 (success) or 500 (exception). There was no way to return 4xx status codes for invalid input because:

1. All return values were serialized and wrapped in Response(200)
2. All exceptions (including HTTPException) were caught and converted to JSONResponse(500)

Changes

Two mechanisms for handlers to control HTTP status codes:

1. Raise HTTPException (the approach from the issue):

from starlette.exceptions import HTTPException

@app.entrypoint
def invoke(payload):
   if not payload.get("prompt"):
       raise HTTPException(status_code=400, detail="Prompt missing")
   return {"message": "ok"}

2. Return a Response object directly:

from starlette.responses import JSONResponse

@app.entrypoint
def invoke(payload):
   if not payload.get("prompt"):
       return JSONResponse({"error": "Prompt missing"}, status_code=400)
   return {"message": "ok"}

Both were mentioned in the issue as expected behavior.

Logging improvements

• HTTPException with 4xx → logs at WARNING
• HTTPException with 5xx → logs at ERROR (matches generic exception severity)
• Returning a Response with 4xx/5xx → logs at WARNING instead of "Invocation completed successfully"

What's unchanged

• Returning a dict/list/string → still wrapped in Response(200)
• Unhandled exceptions → still JSONResponse(500)
• Invalid JSON body → still JSONResponse(400)
• Streaming responses → unaffected

Testing

Verified with 5 scenarios:

Scenario	Expected	Result
raise HTTPException(400)	400	✅
Return dict normally	200	✅
Return JSONResponse(404)	404	✅
raise HTTPException(500)	500	✅
raise ValueError()	500	✅

[jariy17]

nit: this could be part of the if, elif statement above.