docs(EM-49): Define Logging Standards and Structured Logging Configuration

[devin-ai-integration]

Summary

Adds logging standards documentation under docs/logging-standards/ and environment-specific Logback configuration templates under config/logback/. These complement (not duplicate) the existing docs/logging/README.md architecture overview and build on libs/ftgo-logging (EM-43) and libs/ftgo-tracing (EM-42).

Documentation (docs/logging-standards/):

• README.md — index, quick start, integration diagram
• log-levels.md — per-environment log level matrix (dev/staging/prod), level usage guidelines, anti-patterns, sensitive data rules
• json-format.md — canonical JSON schema with required/optional fields, Elasticsearch field mapping
• mdc-standards.md — standard and custom MDC fields, lifecycle management, async propagation patterns (TaskDecorator, CompletableFuture, Kafka)
• log-aggregation.md — KQL query patterns, debugging workflows, Elasticsearch Query DSL examples, alerting thresholds

Logback Templates (config/logback/):

• logback-spring-dev.xml — plain-text colored console, DEBUG root, verbose SQL/framework logging
• logback-spring-staging.xml — JSON console + Logstash TCP, INFO root
• logback-spring-prod.xml — JSON console + Logstash TCP, INFO root, conservative framework levels
• logback-spring-test.xml — plain-text console, WARN root, no ftgo-logging dependency

No existing files modified. Documentation and config-template-only change.

Updates Since Last Revision

Addressed issues flagged in initial review:

• Fixed stray ] character in json-format.md traceId example value
• Removed unused SERVICE_NAME springProperty from dev, staging, and prod templates (the included logback-ftgo.xml fragment uses its own FTGO_SERVICE_NAME property)
• Added clarifying callout in mdc-standards.md Kafka consumer section explaining why manually setting traceId is acceptable there (no HTTP request context for the tracing library to instrument)

Review & Testing Checklist for Human

• Dev template activates on default profile: logback-spring-dev.xml uses <springProfile name="dev,local,default"> — this means DEBUG-level logging fires when no Spring profile is set. Confirm this is the desired team behavior or if default should be removed.
• Logback templates are untested against a real service: No service currently wires these templates. Recommend copying one (e.g. dev) into a service and verifying it loads without errors before wider adoption.
• Docs accuracy spot-check: The log level matrix, MDC field tables, and Kibana query examples are based on the existing libs/ftgo-logging and libs/ftgo-tracing code — worth a quick scan to confirm alignment with actual library behavior.

Suggested test plan:

1. Copy config/logback/logback-spring-dev.xml to a service's src/main/resources/logback-spring.xml
2. Run the service locally with spring.profiles.active=dev
3. Verify console output includes colored plain-text logs with traceId/spanId/requestId MDC fields
4. Repeat with the prod template and spring.profiles.active=prod to verify JSON output

Notes

Requested by: @abj453demo
Link to Devin run

[devin-ai-integration]

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