Fix null assignee handling in Seat model to prevent 500 Internal Server Error

[Copilot]

Problem

Users were encountering a 500 Internal Server Error when accessing the /api/seats endpoint:

500 Internal Server Error – most likely a bug in the app.  
Error: [GET] "/api/seats": 500 Server Error

This occurred when the GitHub Copilot billing seats API returned entries where the assignee field is null. This happens when a user has been removed from the organization but their seat assignment still exists in the system as a deprecated entry.

Root Cause

The Seat model constructor was attempting to access data.assignee.login and data.assignee.id without null checks:

// Before (causing the error)
constructor(data: any) {
    this.login = data.assignee.login;      // ❌ Throws if assignee is null
    this.id = data.assignee.id;            // ❌ Throws if assignee is null
    this.team = data.assigning_team ? data.assigning_team.name : '';
    // ...
}

When data.assignee was null, this resulted in TypeError: Cannot read properties of null (reading 'login'), causing the 500 server error.

Solution

Added null safety checks with appropriate fallback values:

// After (handles null assignee gracefully)
constructor(data: any) {
    this.login = data.assignee ? data.assignee.login : 'deprecated';  // ✅ Safe fallback
    this.id = data.assignee ? data.assignee.id : 0;                   // ✅ Safe fallback
    this.team = data.assigning_team ? data.assigning_team.name : '';
    // ...
}

Changes Made

1. Fixed Seat.ts constructor: Added null checks for data.assignee with sensible fallback values
2. Added comprehensive tests: Created 5 test cases covering various null scenarios
3. Updated mock data: Enhanced sample JSON files to include deprecated seats for better testing

Testing

• ✅ All existing tests continue to pass
• ✅ New tests specifically validate the null assignee scenario
• ✅ Build process completes successfully
• ✅ Mock data includes realistic deprecated seat examples

The fix ensures that deprecated seats (with null assignees) are displayed with login: 'deprecated' and id: 0 instead of causing server crashes.

Fixes #209.

Warning

Firewall rules blocked me from connecting to one or more addresses

I tried to connect to the following addresses, but was blocked by firewall rules:

• api.fontshare.com
  • Triggering command: node (vitest) (dns block)
  • Triggering command: node /home/REDACTED/work/copilot-metrics-viewer/copilot-metrics-viewer/node_modules/.bin/nuxt build (dns block)
• api.fontsource.org
  • Triggering command: node (vitest) (dns block)
  • Triggering command: node /home/REDACTED/work/copilot-metrics-viewer/copilot-metrics-viewer/node_modules/.bin/nuxt build (dns block)
• fonts.bunny.net
  • Triggering command: node (vitest) (dns block)
  • Triggering command: node /home/REDACTED/work/copilot-metrics-viewer/copilot-metrics-viewer/node_modules/.bin/nuxt build (dns block)
• fonts.google.com
  • Triggering command: node (vitest) (dns block)
  • Triggering command: node /home/REDACTED/work/copilot-metrics-viewer/copilot-metrics-viewer/node_modules/.bin/nuxt build (dns block)
• fonts.googleapis.com
  • Triggering command: node (vitest 1) (dns block)
  • Triggering command: node (vitest 2) (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to my firewall allow list

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