fix(micrometer): publish artifact + document okapi.metrics.refresh-interval

[endrju19]

Summary

Follow-up to #27. Two fixes discovered while testing the merged observability changes against a standalone Spring Boot demo app.

1. okapi-micrometer was not being published

The module's build.gradle.kts was missing id(\"buildsrc.convention.publish\"). Without this, the module compiles and ships in source but is not published to Maven Central, so downstream users declaring com.softwaremill.okapi:okapi-micrometer:0.1.0 would get an unresolvable dependency.

Verified by reproducing the issue with ./gradlew publishToMavenLocal: before the fix, every other module appeared in ~/.m2/repository/com/softwaremill/okapi/ except okapi-micrometer. After the fix, all modules publish.

2. okapi.metrics.refresh-interval lacked IDE autocomplete metadata

The new property was not registered in spring-configuration-metadata.json, so users in IntelliJ / VS Code wouldn't get autocomplete or hover docs in application.yml. Same pattern as existing okapi.processor.* and okapi.purger.* entries.

Also added KDoc on OkapiMetricsProperties and a Configuration table to the README Observability section.

Test plan

• ./gradlew publishToMavenLocal -PskipSigning=true produces okapi-micrometer-0.1.0.jar containing both MicrometerOutboxMetrics and OutboxMetricsRefresher
• Demo app at consumer-side (Spring Boot + Postgres + Prometheus actuator) successfully imports okapi-micrometer:0.1.0 and renders all expected metrics on /actuator/prometheus:
  • Counters: okapi_entries_delivered_total, okapi_entries_retry_scheduled_total, okapi_entries_failed_total
  • Timer: okapi_batch_duration_seconds_*
  • MultiGauge: okapi_entries_count{status=...}, okapi_entries_lag_seconds{status=...} (3 status rows each, one query per refresh)
• ./gradlew ktlintCheck clean

Notes

The publish-plugin omission would surface at the next Maven Central release of okapi (i.e. when 0.1.0 artifacts are pushed). Worth catching before then.