Maybe You could set the on_delete option between user and its addresses association.
By default, it will do nothing… Thus I think it is why You get this error.
For this to work, You could look at
https://hexdocs.pm/ecto/Ecto.Migration.html#references/2
and
https://hexdocs.pm/ecto/Ecto.Schema.html#has_one/3
This would be in your addresses migration
add :user_id, references("users"), on_delete: :delete_all
and in the schema
has_one :addresses, Assistant.Web.Address, on_delete: :delete_all
It is not tested, but it might help…
