Problem Description

When creating a user on the $external database user creation fails with the error:
MongoshInvalidInputError: [COMMON-10001] Missing required property: "pwd"

However, users on the $external database do not have a password.

Steps to Reproduce

Try creating a user for X509 authentication:

xdb = db.getSiblingDB('$external');
xdb.createUser(
    {
        user: "CN=Client,OU=Public-Client,O=MongoDB",
        roles: [
            {role: "root", db: "admin"},
        ]
    }
);

Expected Results

The user is created successfully.

Actual Results

An error is thrown:
MongoshInvalidInputError: [COMMON-10001] Missing required property: "pwd"