[CAT-4227] Past OLA Test Sessions - Celery Task Refactor/Improvements (Celery Task - Handle Past Test Sessions)

Description

This PR is introducing the following changes:

• refactoring and improved the handle past test sessions celery task to get rid of OLA sessions that no longer have links to any consumed reservation code entries
• adding new manual trigger of the handle past test session on the super user dashboard
• future-proofing the assign/unassign scorer to candidate logic by replacing gets with filters and adding try except to make sure the proper data exists

JIRA Ticket Number

Parent Task(s):

• CAT-4227

Type of change

• New feature
• Bug fix
• Accessibility Patch
• Vulnerability Fixes
• Documentation update
• Code cleanliness or refactor
• CICD Tests
• Translation

Screenshots / GIFs (gifcap)

Manual Trigger - Super User Dashboard:

Testing

(Additional info for testing if needed)

Checklist

• I have updated model structure and/or static data ==> Create new MSSQL Image
• I have added or updating documentation related to my code changes
• I have commented my code
• I do not have any compiler warnings/errors
• I have added CICD tests or created a JIRA to do it
• I have researched WCAG2.1 accessibility standards and met them in this PR
• I have ensured that my changes look good on various screen sizes (minimum 1024 x 768)
• I have translated related text or created a JIRA to do it
• I have given or scheduled a demo of the PR to/with the Product Owner
• I have labeled my merge request with the right release number
• I have linked my PR to all related Jira tasks
• I have updated the status of all related Jira tasks