[Feature] Improve candidate assessmentStatus data

[JamesHuf]

🤖 Resolves #12421

👋 Introduction

Updates the way the assessmentStatus field for PoolCandidates is calculated to allow a slightly more detailed status to be shown to candidates.

🕵️ Details

Prevents assessmentSteps showing up in the assessmentStatus.assessmentStepStatuses field on PoolCandidates until they have at least one assessmentResult to make it possible for candidates to tell if the step has started to be assessed or not.

🧪 Testing

1. Confirm tests still pass
2. Create and submit an application and update it's assessment progress confirming it's possible to tell if a step has begun assessment by whether it shows in the assessmentStepStatuses field.

Useful query:

query PoolCandidate {
  poolCandidate(id: userId) {
      assessmentStatus {
        assessmentStepStatuses {
          step
          decision
        }
        overallAssessmentStatus
        currentStep
      }
    }
}

🚚 Deployment

After deployment run the artisan command to recalculate assessment statuses:

php artisan app:sync-assessment-status