ensure error reporting follows the GCP expected format

in GKE logs sent to stdout and stderr are sent to Cloud Logging, original log entry's severity level is not retained.
Spring Boot uses Slf4J logging API and Logback logger by default. You can user [Spring Cloud GCP's Logging Starter](https://cloud.spring.io/spring-cloud-static/spring-cloud-gcp/current/reference/html/#stackdriver-logging) to use pre-configured Logback appenders to produce Structured JSON logs, or send the log via the Cloud Logging API.

see https://spring-gcp.saturnism.me/app-dev/observability/logging#logback for more detail

Start by reviewing the GKE stdout and stderr logging path and the linked Spring Cloud GCP Logging Starter and Logback guidance. Determine how Spring Boot's Slf4J and Logback configuration should preserve the original severity in Cloud Logging, then verify that emitted entries use the expected GCP format and retain severity.

Written by the indexing model from the issue text.