Add tests for what happens on `PendingMembershipExpired`

It seems that function expire_pending_memberships which triggers T::OnEvent::on_event(&sp_membership::Event::PendingMembershipExpired lead to Self::dispatch_idty_call(pallet_identity::Call::remove_identity no matter the instance of the membership pallet (simple membership or smith membership).

We have to add tests to cover this behavior and make sure that pending smith membership expiration does not kill the associated identity.

changed milestone to %runtime-800

added P2-asap label

assigned to @bgallois

changed due date to December 08, 2023

The bug was already identified in #51 (closed) but only partially fixed.

mentioned in issue #156 (closed)

marked this issue as related to #141

unassigned @bgallois

assigned to @HugoTrentesaux

removed due date December 08, 2023

mentioned in merge request !215 (merged)

closed with merge request !215 (merged)