In some XRay instances, when importing test execution results Xray format, the Assignee field is not set up on the screen

Short Description: In some XRay instances, when importing test execution results Xray format, the Assignee field is not populated on the screen

Steps to Reproduce:

1 - Create a POST request to import test execution results of Xray format, using the following endpoint (...)/api/v1/import/execution/

2 - In the info section, pass the "user" input with name "admin" and send the request

3 - Do the previous steps, but enter the name of a user that does not exist

4 - Do the previous steps, but put the account id in the user input field

Actual Result: The test execution is created but unassigned when searching for it 

Expected Result: To make it consistent with GDPR guidelines, we should now pass the account if of the user to whom we want to assign the issue and its correspondent name should be displayed in the Assignee field