fix(chart): add error logging to /api/v1/chart/data endpoint

[rebenitez1802]

SUMMARY

Add error-level logging to all failure paths in the chart data API (/api/v1/chart/data) to help diagnose intermittent 400 BAD REQUEST failures during CSV exports.

TESTING INSTRUCTIONS

1. Trigger a CSV export from a dashboard — should succeed with no extra logs
2. Simulate failures (malformed form_data, missing datasource, permission denied) — error logs should appear with request context
3. Run existing chart data API tests — no regressions expected

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[EnxDev]

When form_data is present but unparseable, this block fires after the except above has already logged. A single parse failure produces two logger.error entries in the log, which could be confusing when correlating events.

[bito-code-review]

Yes, the code change introduces duplicate logging for unparseable form_data. The except block logs an error on JSONDecodeError, and then the subsequent if json_body is None block logs another error, leading to two entries for a single failure.

superset/charts/data/api.py

try:
                json_body = json.loads(request.form["form_data"])
            except (TypeError, json.JSONDecodeError):
                logger.error(
                    "Failed to parse form_data JSON: "
                    "content_type=%s, content_length=%s, form_data_length=%s, "
                    "referrer=%s",
                    request.content_type,
                    request.content_length,
                    len(request.form.get("form_data", "")),
                    request.referrer,
                )
            if json_body is None:
                logger.error(
                    "Chart data request rejected: json_body is None. "
                    "is_json=%s, content_type=%s, content_length=%s, "
                    "has_form_data=%s, referrer=%s",
                    request.is_json,
                    request.content_type,
                    request.content_length,
                    bool(request.form.get("form_data")),
                    request.referrer,
                )
                return self.response_400(message=_("Request is not JSON"))