Collect config environment variable usage metric

Collect basic metrics about a DAST scan. The scan_uuid allows joining to other DAST scan metrics.

{
	"event": "collect_dast_scan_config_variable_metrics_from_pipeline",
	
	// Columns (join, filter, fast)
	
	"property": "scan_uuid",          // join: Allows joining
	"label": "DAST_CONFIG_VARIABLE"   // fast: Config environment variable
}

Implementation Plan

1. Define new internal event in monolith
2. Whitelist event name for use in security report
3. Populate event in DAST security report
4. Validate event data is populating in snowflake