Add Config to disable Auth Transfers. (#7843)

* Add Config to disable Auth Transfers.

* Set config ExperimentalEnableAuthenticationTransfer behind an E20 license restriction

app/ldap.go

@@ -39,6 +39,10 @@ func (a *App) TestLdap() *model.AppError {
 }
 
 func (a *App) SwitchEmailToLdap(email, password, code, ldapId, ldapPassword string) (string, *model.AppError) {
+	if utils.IsLicensed() && !*a.Config().ServiceSettings.ExperimentalEnableAuthenticationTransfer {
+		return "", model.NewAppError("emailToLdap", "api.user.email_to_ldap.not_available.app_error", nil, "", http.StatusForbidden)
+	}
+
 	user, err := a.GetUserByEmail(email)
 	if err != nil {
 		return "", err
@@ -71,6 +75,10 @@ func (a *App) SwitchEmailToLdap(email, password, code, ldapId, ldapPassword stri
 }
 
 func (a *App) SwitchLdapToEmail(ldapPassword, code, email, newPassword string) (string, *model.AppError) {
+	if utils.IsLicensed() && !*a.Config().ServiceSettings.ExperimentalEnableAuthenticationTransfer {
+		return "", model.NewAppError("ldapToEmail", "api.user.ldap_to_email.not_available.app_error", nil, "", http.StatusForbidden)
+	}
+
 	user, err := a.GetUserByEmail(email)
 	if err != nil {
 		return "", err