Using Assets External Imports to try and update an Object with a User Attribute will fail despite the User Attribute not being related to the External Import

Issue Summary

When running External Imports to import Assets Objects, if an Object has a User Attribute added manually, separately from the External Import, then when the External Import tries to update the Object for unrelated Attributes, it will fail with an error that the User Attribute's value doesn't exist in Jira.

Steps to Reproduce

1. Enable External Import
2. Push Object mappings
3. Manually add an attribute of type User to the Object Type via the User Interface - Leave the User Attribute Empty
4. Run the import (this will run successfully)
5. Add a value to the previously created User Attribute on the Object Type
6. Manually update an object, changing any other attribute that is present in the import mapping
7. Re-run the import, the import will identify that 1 object needs to be updated

Expected Results

The Object will be updated with the non-User Attribute Values.

Actual Results

The import will fail to update the object due to the User attribute.
Example of the error:
Error: User(s) (<AtlassianAccountID>) not found in Jira. [Object (Label: <object-label>, Id: <object-id>)].

Workaround

Create a User Object that has the User Attribute to go in place of the User on relevant Objects via an Object Attribute. i.e. create a layer of abstraction between the Object that needs to be linked to the User and the User.

For example, instead of having a Workstation Object with a User Attribute of Owner, have the Owner Attribute be an Object Attribute that links to a static User Object.

This User Object doesn't need to be updated, typically, so it won't affect External Imports trying to update Assets Object Attributes, but it will have a User Attribute that links to the User's actual Atlassian Account.