Add lightweight bounded background job queue

[balajibashyam]

Summary

Adds a minimal .NET 10 companion sample for the .NET 8 Background Jobs: IBackgroundTaskQueue, BackgroundService & Production-Ready Patterns tutorial.

What's included

• New sample: dotnet-8-essentials/background-jobs-hostedservice-queues/ — 14 files

  • Typed EmailJob record, bounded Channel<EmailJob> with asynchronous backpressure
  • BackgroundService consumer with fresh async DI scope per job
  • Scoped IEmailJobHandler with deterministic fake processing
  • In-memory job tracker with Queued/Running/Succeeded/Failed/Canceled states
  • Minimal API: POST /jobs/email (202), GET /jobs/{jobId}, GET /jobs/queue
  • Request validation, safe failure messages, cancellation propagation
  • 8 xUnit v3 integration tests proving FIFO, backpressure, completion drain, fresh scopes, failure isolation, cancellation, API 202, and validation 400

• Root README: New sample row in the samples table + updated repository structure tree

• GitHub Actions: New test-background-job-queue job in the shared workflow; path filters updated for push and pull_request

Deliberately omitted (stays in the full tutorial)

Retries, Polly, dead-letter storage, schedules, metrics exporters, health probes, durable brokers, databases, real email delivery, multiple workers, parallel processing.

Versions

• .NET SDK: 10.0.302
• Microsoft.AspNetCore.Mvc.Testing: 10.0.10
• xunit.v3: 3.2.2
• Application NuGet dependencies: zero

Validation

• dotnet restore — passed
• dotnet build --configuration Release — passed (0 errors, 0 warnings)
• dotnet test --configuration Release — passed (8/8)
• Security scan — clean
• Runtime smoke test — root JSON exact match, queue JSON exact match, enqueue returned 202, invalid request returned 400