Add lightweight passkey identity sample

[balajibashyam]

Summary

Adds a minimal .NET 10 companion sample for the Passkeys in ASP.NET Core Identity (.NET 10): Build a Passwordless-First Web App with WebAuthn tutorial.

What's included

• New sample: aspnet-core/passkey-first-identity/ — 15 files

  • .NET 10 ASP.NET Core Identity with schema version 3
  • SQLite with EnsureCreated schema bootstrapping
  • Development-only bootstrap user (demo@example.com)
  • Bootstrap password login endpoint
  • Passkey creation-options, registration, request-options, sign-in, and listing endpoints
  • Antiforgery validation on every state-changing passkey POST
  • Minimal browser page and WebAuthn JavaScript using native JSON serialization
  • 6 server-side integration tests (auth boundary, antiforgery, login flow, passkey listing, domain config)

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

• GitHub Actions: New test-passkey-identity job in the shared workflow; path filters updated

Deliberately omitted (stays in the full tutorial)

Conditional UI, username-less sign-in, passkey rename/delete, password removal, recovery, email, attestation policy, FIDO metadata, browser automation, production deployment.

Versions

• .NET SDK: 10.0.302
• Microsoft.AspNetCore.Identity.EntityFrameworkCore: 10.0.10
• Microsoft.EntityFrameworkCore.Sqlite: 10.0.10
• xunit.v3: 3.2.2

Validation

• dotnet restore — passed
• dotnet build --configuration Release — passed (0 errors)
• dotnet test --configuration Release — passed (6/6)
• Application starts and responds to all endpoints
• Security scan — clean
• No generated folders, databases, secrets, private keys, or private paths committed