refactor(api): move postgres error handling into a separate function in a separate file

backend/api/utils.go

@@ -0,0 +1,22 @@
+package api
+
+import (
+	"strconv"
+
+	"github.com/jackc/pgx/v5/pgconn"
+)
+
+func HandlePgError(err error) (int, string) {
+	pgErr, ok := err.(*pgconn.PgError)
+	if !ok {
+		return 500, err.Error()
+	}
+	statusStr := pgErr.Message[:3]
+	message := pgErr.Message[4:]
+	status, err := strconv.ParseInt(statusStr, 10, 0)
+	if err == nil {
+		return int(status), message
+	} else {
+		return 500, message
+	}
+}