Field to use for user id

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I don’t see ‘sub’.
I’m getting back this

{
    "email_verified": true,
    "email": "someone@gmail.com",
    "username": "someusername",
    "updated_at": "2019-07-10T21:59:16.105Z",
    "user_id": "auth0|5a1b61913...",
    "name": "someone@gmail.com",
    "picture": "https://s.gravatar.com/avatar/f81...png",
    "nickname": "someone",
    "identities": [
        {
            "user_id": "6d1a61..",
            "provider": "auth0",
            "connection": "Username-Password-Authentication",
            "isSocial": false
        }
    ],
    "created_at": "2019-07-01T19:40:01.385Z",
    "last_ip": "...",
    "last_login": "2019-07-10T21:59:16.105Z",
    "logins_count": 6,
    "blocked_for": [],
    "guardian_authenticators": []
}

I see user_id there. Don’t know how I missed it before.
Is there significance to the ‘auth0|’ part. Do you recommend keeping that part of the string or parsing it out?