chore: add healthz point

store/db/postgres/common.go

@@ -0,0 +1,18 @@
+package postgres
+
+import (
+	"fmt"
+	"strings"
+)
+
+func placeholder(n int) string {
+	return "$" + fmt.Sprint(n)
+}
+
+func placeholders(n int) string {
+	list := []string{}
+	for i := 0; i < n; i++ {
+		list = append(list, placeholder(i+1))
+	}
+	return strings.Join(list, ", ")
+}