Added default map back to the importer

[snipe]

This is basically a reversal of d228b7f, but with some added comments. When we refactored the importer to make it more Livewire-y, we pulled out a variable that we thought we didn't need anymore. It's only come up recently because some folks use the cli importer a lot more than we realized, and that commit broke the cli for them.

We do need to find a way to make this less duplicative, either by importing the variables from the Livewire side, or vice versa. This should at least fix the cli importer for now, and won't interfere with the GUI importer.

[what-the-diff]

PR Summary

• Addition of User ID attribute
  A protected user_id attribute was added in Importer.php. This inclusion allows for the identification of the specific user making particular changes, enhancing traceability.

• Inclusion of Update State attribute
  Another attribute named updating has been inserted. This enables the system to better recognize and handle instances when an update is ongoing, improving system responsiveness.

• Introduction of Default Field Map
  A $defaultFieldMap array has been introduced with several key-value pairs. The addition of this attribute improves the mapping and handling of fields and their default values, thereby making operations more seamless and efficient.