Identity: Use TimeProvider for Passkey CreatedAt

[Vladik29w]

Identity: Use TimeProvider for Passkey CreatedAt

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Summary of the changes (Less than 80 chars)
Use TimeProvider instead of DateTime.UtcNow in PasskeyHandler.

Description

This PR addresses the issue where passkey registration was hardcoded to use DateTime.UtcNow. It updates PasskeyHandler to use the injected TimeProvider instead to set the CreatedAt value, which allows for proper unit testing of time-dependent logic.

Test cases have been updated/added to verify the behavior using a fake time provider.

Fixes #66477

[Copilot]

Pull request overview

This PR updates ASP.NET Core Identity’s passkey registration flow to respect a TimeProvider (when available) instead of hardcoding DateTime.UtcNow for the passkey CreatedAt timestamp, enabling deterministic time-dependent tests.

Changes:

• Update PasskeyHandler to obtain the current UTC time via TimeProvider resolved from request services (with fallback).
• Add/adjust unit test coverage to validate CreatedAt is sourced from a fake TimeProvider.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/Identity/Core/src/PasskeyHandler.cs	Uses TimeProvider (via HttpContext.RequestServices) when setting UserPasskeyInfo.CreatedAt.
src/Identity/test/Identity.Test/Passkeys/PasskeyHandlerAttestationTest.cs	Adds a test that sets a fake time provider and asserts CreatedAt matches it.

[Vladik29w]

@dotnet-policy-service agree

[dotnet-policy-service]

Thanks for your PR, @Vladik29w. Someone from the team will get assigned to your PR shortly and we'll get it reviewed.