* SAML: add default params for role and team sync

* SAML: add org_mapping option

* SAML: support allowed_organizations option

* Chore: expose RedirectWithError from HTTPServer

* Chore: return RedirectResponse (fix superfluous response.writeheader message)

* HTTPServer: expose ValidateRedirectTo() and CookieOptionsFromCfg()

* Config: move SAML section to the enterprise