Behaviour for entry persistence.
Summary
Callbacks
@callback get_entry(term()) :: {:ok, CommBus.Entry.t()} | {:error, :not_found}
@callback list_entries(keyword()) :: {:ok, [CommBus.Entry.t()]} | {:error, term()}
@callback store_entry(CommBus.Entry.t()) :: {:ok, CommBus.Entry.t()} | {:error, term()}