Node Exporter enhancement request

Number of database users should be something the exporter scrap for as well. Specially if enterprise starts going the hashicorp vault way for user and credentials.

Start by locating the exporter’s metric collection entry point and any existing tests for scraped Couchbase metrics. Determine how a database-user count should be represented in the Prometheus output, then add coverage showing the metric is exported with the expected value.

由索引模型根据 Issue 内容生成。