Minimal length for User Id

We are using Amplitude Node SDK for events reporting.
While implementing, we've noticed that when trying to log an event and attach it a `user id` that its length is lower than 5 chars, we get an error:
`Status code: 400, Status: invalid, Response body: {"error":"Invalid id length for user_id or device_id", ...}`.
To overcome this error, we concatenated 5 leading spaces, after that, the error has gone and the `logEvent` function succeeded (we also validated that the leading spaces are trimmed in the Amplitude analytics site).

Could you please fix this issue, to avoid the 5 leading spaces trick?

- SDK Version: `1.5.3`
- Node version: `15.6.0`