fix: production CPU/GC incident - unconditional log masking, missing schema cache, default DEBUG logging

[hongwei1]

Summary

Root-caused a production incident (sustained 600% CPU, Full-GC thrashing, eventual service timeout) on a sandbox instance. Three independent fixes, bundled together since they trace back to the same investigation and are small enough to review as a set.

1. MdcLoggable (code/util/Helper.scala) ran SecureLogging.maskSensitive (~19 regex passes) and Redis-shipping JSON serialization unconditionally on every info/warn/error/debug/trace call, before checking whether the underlying logger or Redis would even consume the message -- and, once gated, still ran that work inline on the calling thread. On the http4s/cats-effect request path that's often a fiber-managed worker; non-yielding CPU-bound work there looks identical, to the runtime's own starvation detector, to genuine blocking I/O, and its response (spinning up compensating worker/blocker threads that are never reclaimed) links directly to a heap dump showing hundreds of threads each holding a private Scala-reflection symbol-table cache. Fixed by gating on isXEnabled/RedisLogger.shouldShip (new redis_logging_min_level prop, default INFO) and dispatching the actual work onto a small dedicated ExecutionContext instead of the calling thread.

2. JsonSchemaGenerator.messageDocsToJsonSchema had no cache of its own, walking every message type's field tree via Scala runtime reflection on every call; its caller's Redis-backed cache silently falls through to a full recompute on any Redis failure. Added an in-process memoization (Guava-backed, no Redis dependency) alongside the existing one, using the same pattern already proven correct by Helper.getRequiredFieldInfo. Independent hardening for a real gap in this file -- not confirmed as this incident's cause; JsonSchemaGenerator doesn't appear anywhere in this incident's JFR execution samples.

3. logback.xml.example sat inert (Logback only auto-loads files named exactly logback.xml) with root level hard-coded to DEBUG; deployments that never manually copied it over fell back to Logback's own built-in DEBUG-to-console default. Renamed to logback.xml so it's actually loaded, and changed the level to ${LOG_LEVEL:-INFO}: verbose logging should be an explicit per-environment opt-in, not the default every deployment silently pays for.

Test plan

• mvn -pl obp-commons,obp-api -am compile -DskipTests -o -- BUILD SUCCESS
• RedisLoggerShouldShipTest, MdcLoggableDispatchTest, JsonSchemaGeneratorCacheTest, MessageDocsJsonSchemaTest, LogbackDefaultLevelTest -- all passing individually
• Full local suite (run_tests_parallel.sh), run twice -- 3919 tests / 0 failures / 0 errors / 18 skipped, all shards passing
• CI -- all checks green

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

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

See analysis details on SonarQube Cloud

[hongwei1]

Closing to reopen from a cleanly-named branch (the old branch name referenced a client name that shouldn't appear in this repo's history). Same commit, same content, re-opened here.