PostgreSQL Exporter

The PostgreSQL Exporter scrapes PostgreSQL server metrics and exports them
as Prometheus metrics.

Key features:
- Exports PostgreSQL server statistics as Prometheus metrics
- Supports PostgreSQL 13, 14, 15, 16, 17, and 18
- Configurable via DSN connection string

Default ports:
- Metrics endpoint: 9187

Configuration:
- snap set postgres-exporter web.listen-port=PORT
- snap set postgres-exporter data-source.uri=localhost:5432/postgres?sslmode=disable
- snap set postgres-exporter data-source.user=postgres
- snap set postgres-exporter data-source.password=password