Redirect if the license can’t be found

[snipe]

This is a small fix that prevents a rollbar/500 error from triggering if someone hits the demo while the seeders are running or have just run. Basically, someone trying to check out a license that no longer exists since the DB reset itself (as it does on the demo, on a cron.)

Should not affect any normal circumstances. We're already doing this check on the checkout save method.

[what-the-diff]

PR Summary

• Ensured Authorized Access Before License Check
  The system now performs a user authorization check before it even checks if a requested license is valid. This fortifies our security, ensuring only approved users can perform license checks.

• Added License Availability Verification
  The system will now verify if there are available seats (unoccupied access points) for a specific license. This update should ensure users can only access licenses with spare seats, therefore enhancing our license management.

• Error Redirect for Non-existent License
  If a searched license does not exist, the system will now redirect the user to an error message. This should streamline the user experience, ensuring the user knows if a license search yields no results.

• Removed Redundant Authorization Check
  The authorization check post license validity verification has been removed as it was redundant. This could enhance system efficiency by reducing unnecessary tasks.

• Added a View Display Upon License Check Completion
  When the license check is completed, the system will now present a 'licenses/checkout' view, with data about the relevant license. This feature offers users a better visualization, allowing them to see license details immediately upon check completion.