## 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
settings = cast(Dict, copy.deepcopy(MOCK_SETTINGS))
        settings["SOCIAL_AUTH_SAML_ENABLED_IDPS"]["posthog_custom"]["attr_first_name"] = "urn:oid:2.5.4.42"
        settings["SOCIAL_AUTH_SAML_ENABLED_IDPS"]["posthog_custom"]["attr_last_name"] = "urn:oid:2.5.4.4"
        settings["SOCIAL_AUTH_SAML_ENABLED_IDPS"]["posthog_custom"]["attr_email"] = "urn:oid:0.9.2342.19200300.100.1.3"
        self.client.logout()
        self.organization.domain_whitelist = ["posthog.com"]
        self.organization.save()
        with self.settings(**settings):
            response = self.client.get("/login/saml/?idp=posthog_custom")
        self.assertEqual(response.status_code, status.HTTP_302_FOUND)
        _session = self.client.session
        _session.update(
            {"saml_state": "ONELOGIN_87856a50b5490e643b1ebef9cb5bf6e78225a3c6",}
        )