### Context
User (who has create a workspace and deleted it) can't create new
workspace because after deleting his previous workspace, user has not
been soft deleted.
There is several cases where user should be soft deleted :
1/ if user delete his account
2/ if a user's workspace is deleted + user has no other workspace
3/ If a workspaceMember is removed + user has no other workspace
### Solution
In `handleRemoveWorkspaceMember` method (logic used in the 3 cases),
soft delete user when removing the last userWorkspace
closes#9728
Co-authored-by: etiennejouan <jouan.etienne@gmail.com>
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