Centralize daypart key canonicalization

internal/briefing/derived_daypart_summaries_module.go

@@ -400,7 +400,7 @@ func multipleSummaryDates(summaries []forecast.DailySummary) bool {
 }
 
 func daypartKey(daypart forecast.DaypartSummary, prefixDate bool) string {
-	key := normalizedKey(daypart.Name)
+	key := forecast.CanonicalDaypartKey(daypart.Name)
 	if key == "" {
 		key = "unnamed"
 	}
@@ -409,21 +409,3 @@ func daypartKey(daypart forecast.DaypartSummary, prefixDate bool) string {
 	}
 	return daypart.Period.Start.Format(timeutil.DateLayout) + "_" + key
 }
-
-func normalizedKey(value string) string {
-	lower := strings.ToLower(strings.TrimSpace(value))
-	var out strings.Builder
-	lastUnderscore := false
-	for _, r := range lower {
-		if unicode.IsLetter(r) || unicode.IsDigit(r) {
-			out.WriteRune(r)
-			lastUnderscore = false
-			continue
-		}
-		if !lastUnderscore {
-			out.WriteByte('_')
-			lastUnderscore = true
-		}
-	}
-	return strings.Trim(out.String(), "_")
-}