Added test cases around modifying user groups via api

[marcusmoore]

Description

This PR adds two test cases around functionality in the api's user controller for modifying user groups.

Type of change

• Other...

[what-the-diff]

PR Summary

• Introduction of new dependencies
  The file has been updated to import the 'Group' model from the 'App\Models' path. The 'Group' model is helpful for managing user group related features.

• Addition of New Test Methods for Super User Verification
  Two new test methods have been added for security purposes.

  1. testUserGroupsAreOnlyUpdatedIfAuthenticatedUserIsSuperUser makes sure that user group roles are only altered if the user is certified as a 'Super User'.
  2. testUserGroupsCanBeClearedBySuperUser ensures that only 'Super Users' possess the ability to clear all group affiliations linked to a particular user.

• Enhancement of Existing Test Function
  An existing test function has been supplemented with additional assertions. These assertions help in testing a condition or predicting a result, providing more robust functionality to our system's checks and balances.