tables: expose loggers actuator endpoint for dynamic log level control

[cbb330]

Summary

Adds the Spring Boot Actuator /actuator/loggers endpoint to the tables-service, enabling dynamic log level changes at runtime without pod restarts or deployment changes.

Changes

• Client-facing API Changes
• Internal API Changes
• Bug Fixes
• New Features
• Performance Improvements
• Code Style
• Refactoring
• Documentation
• Tests

Added to services/tables/src/main/resources/application.properties:

management.endpoints.web.exposure.include=health, shutdown, prometheus, beans, loggers
management.endpoint.loggers.enabled=true

This exposes POST /actuator/loggers/{name} to set any logger to DEBUG (or reset it) on a live pod without restarting. Intended for incident use to activate targeted diagnostic logging — for example the loggers in application-hdfs-diagnostics.properties — on a single replica without modifying the deployment or replicaset.

Testing Done

• Manually Tested on local docker setup. Please include commands ran, and their output.
• Added new tests for the changes made.
• Updated existing tests to reflect the changes made.
• No tests added or updated. Please explain why. If unsure, please feel free to ask for help.
• Some other form of testing like staging or soak time in production. Please explain.

Local bootRun:

./gradlew :services:tables:bootRun --args='--server.port=18081'

# Endpoint appears in actuator index
GET http://localhost:18081/actuator
→ includes "loggers" and "loggers-name" hrefs

# Set a logger to DEBUG
POST http://localhost:18081/actuator/loggers/org.apache.hadoop.hdfs.DFSClient
Content-Type: application/json
{"configuredLevel": "DEBUG"}
→ HTTP 204

# Verify it took effect
GET http://localhost:18081/actuator/loggers/org.apache.hadoop.hdfs.DFSClient
→ {"configuredLevel": "DEBUG", "effectiveLevel": "DEBUG"}

Test cluster:

Deployed to the test cluster via internal build. Verified from inside the running pod:

kubectl exec <pod> -c tables-service -- \
  curl -s http://localhost:8080/actuator | python3 -m json.tool

{
    "loggers-name": {"href": "http://localhost:8080/actuator/loggers/{name}", "templated": true},
    "loggers":      {"href": "http://localhost:8080/actuator/loggers", "templated": false}
}

All log levels (OFF, FATAL, ERROR, WARN, INFO, DEBUG, TRACE) available via GET /actuator/loggers.

Why no new tests: Configuration-only change (application.properties). The actuator auto-configuration is covered by Spring Boot's own test suite; no functional code paths were modified.

Additional Information

• Breaking Changes
• Deprecations
• Large PR broken into smaller PRs, and PR plan linked in the description.

[cbb330]

Note: the management.endpoints.web.exposure.include change from this PR is included in #511 (which also does the broader SLF4J/log4j unification needed to make the loggers endpoint actually work end-to-end). If #511 merges first, this PR will need to drop the application.properties change to avoid a conflict.