iceberg kafka metrics reporter

[blcksrx]

Description

The KafkaMetricsReporter is a custom implementation of the MetricsReporter interface that allows reporting Iceberg metrics to a Kafka topic. This reporter is designed to serialize metrics reports into JSON format and send them as Kafka messages.

Motivation

This change introduces to address that gap by enabling:

• Observable Metrics Pipelines: Metrics like ScanReport and CommitReport can now be serialized and emitted to a Kafka topic in real-time, making them consumable by monitoring systems, dashboards, or alerting tools.
• Event-Driven Integration: By pushing metrics into Kafka, Iceberg actions can now trigger downstream workflows, such as audits, data lineage tracking, or compaction jobs via Kafka consumers.

Usage

To use the KafkaMetricsReporter, configure the following properties in your catalog:

metrics-reporter-impl=org.apache.iceberg.experimental.KafkaMetricsReporter
metrics-reporter.kafka.bootstrap.servers=localhost:9092
metrics-reporter.kafka.topic=iceberg-metrics

[blcksrx]

@nastra appreciate your review and feedback