## Is your feature request related to a problem?

Currently if you login with SAML and you don't have an account on the PostHog instance one of two things happen: a) either a new account is created **if the email matches the domain whitelist** or b) you get turned down at the door. Yet after some thought, the point of SAML is that you manage user provisioning in a separate centralized system, so we shouldn't have the extra domain check. 

## Describe the solution you'd like

If a user logins through SAML and their account doesn't exist, create it automatically, regardless of whether it matches the domain whitelist.


## Describe alternatives you've considered

Keeping as is.

## Additional context

There's a complicating factor which is that SAML login is instance-based yet user signup is organization-based, so there's the edge case of an instance having multiple orgs. Should the user then be signed up to all organizations?

#### *Thank you* for your feature request – we love each and every one!

ee/api/test/test_authentication.py
import copy
import os
from typing import Dict, cast
import pytest
from django.conf import settings
from django.core.exceptions import ValidationError
from freezegun.api import freeze_time
from rest_framework import status
from social_core.exceptions import AuthFailed
from ee.api.test.base import APILicensedTest
from posthog.models import User
from posthog.models.organization import OrganizationMembership
MOCK_SETTINGS = {
    "SOCIAL_AUTH_SAML_SP_ENTITY_ID": "http://localhost:8000",
    "SAML_CONFIGURED": True,
    "AUTHENTICATION_BACKENDS": settings.AUTHENTICATION_BACKENDS + ["social_core.backends.saml.SAMLAuth",],
    "SOCIAL_AUTH_SAML_ENABLED_IDPS": {
        "posthog_custom": {
            "entity_id": "http://www.okta.com/exk1ijlhixJxpyEBZ5d7",
            "url": "https://idp.hogflix.io/saml",
            "x509cert": """MIIDqDCCApCgAwIBAgIGAXtoc3o9MA0GCSqGSIb3DQEBCwUAMIGUMQswCQYDVQQGEwJVUzETMBEG
    A1UECAwKQ2FsaWZvcm5pYTEWMBQGA1UEBwwNU2FuIEZyYW5jaXNjbzENMAsGA1UECgwET2t0YTEU