Resolves#34103
The SSO invite acceptance page submitted a create-user request without
the invitee's email, because it read `email` from the URL query string
which the invite email link never populates. To resolve this the email
was loaded by calling GET /api/_version_/fleet/invites/{token} endpoint.
As part of this fix, the ConfirmSSOInvite components were refactored
from 'classical' components to functional components.
Juan Fernandez
2c7bb2f6eb