Check that the user exists before trying to print

[snipe]

This is likely more important for the demo since we re-seed that info frequently, but this just does a redirect if the user doesn't exist anymore versus 500ing. Fixed RB-3840.

[what-the-diff]

PR Summary

• Improvement of the Print Inventory Functionality
  The 'printInventory' function contained within Users' management has been upgraded. It now checks if the user ID provided actually exists before proceeding. This is meant to ensure that an error isn't thrown when an unknown or nonexistent user ID is entered.
• Notification Upon User Absence
  In case a user does not exist, the system will not crash or hang. Instead, an appropriate redirection is made back to users' listing area and an error message is displayed. This guides you to the right place if the person you're searching hasn't signed up yet.
• Enhanced Data Retrieval Method
  If a user is found, the enhanced 'printInventory' method retrieves more user-related data, such as assets, accessories, consumables, and licenses. This change is aimed to provide a comprehensive inventory view for each user.
• Removal of Author Annotation
  The author annotation that had no functional impact but increased clutter in the 'UsersController.php' file was removed, ensuring cleaner, leaner, and more efficient code.