improve numeric only id detection

We used `strconv.Atoi` to see if the truncated (12 first chars) on the ID was numeric only.

It works only for small numbers like `strconv.Atoi(001456718841)` won't return any error, so this mean is't a number and we retry generation an ID.

The issue is with big numbers like `strconv.Atoi(901456718841)` will return an error, because it can't fit inside an int, but we will consider it's not a number.

We should make sure it can't fit into an `int64`.

I believe it'll fix #4557