Fix: Extract non-JSON error body

[vostres]

Before:
When the inference service returns a non-JSON response, the actual error is masked by a parsing failure.

Caused by: java.lang.IllegalArgumentException: Could not process JSON error object
Caused by: com.fasterxml.jackson.core.JsonParseException:
Unrecognized token 'dial'

After:
The original error is preserved.

Caused by: com.bakdata.kserve.client.InferenceRequestException:
Inference request failed: 502:
dial tcp 127.0.0.1:8080: connect: connection refused

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud