## 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
def test_can_get_saml_metadata(self):
        OrganizationMembership.objects.filter(organization=self.organization, user=self.user).update(
            level=OrganizationMembership.Level.ADMIN
        )
        with self.settings(**MOCK_SETTINGS):
            response = self.client.get("/api/saml/metadata/")
        self.assertEqual(response.status_code, status.HTTP_200_OK)
        self.assertTrue("/complete/saml/" in response.content.decode())
    def test_need_to_be_authenticated_to_get_saml_metadata(self):