Added AAGUID accessor to Credential and AttestationObject structs

[samalone]

The purpose of adding aaguid accessors is to allow a server to map the ID to a provider name using tables like those on https://github.com/passkeydeveloper/passkey-authenticator-aaguids.

[Copilot]

Pull request overview

This PR adds convenient accessor properties for the Authenticator Attestation Globally Unique Identifier (AAGUID) to the Credential and AttestationObject structs. The AAGUID is a 128-bit identifier that allows servers to identify authenticator make and model, enabling them to map these identifiers to provider names using public registries.

Key Changes:

• Added public aaguid computed property to Credential that delegates to the underlying attestation object
• Added public aaguid computed property to AttestationObject that extracts the AAGUID from authenticator data
• Added comprehensive test coverage for both custom AAGUIDs and the default anonymous AAGUID behavior

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
Sources/WebAuthn/Ceremonies/Registration/Credential.swift	Added public aaguid computed property that delegates to attestationObject.aaguid for convenient access
Sources/WebAuthn/Ceremonies/Registration/AttestationObject.swift	Added public aaguid computed property that extracts AAGUID from authenticatorData.attestedData
Tests/WebAuthnTests/WebAuthnManagerRegistrationTests.swift	Added two parameterized tests covering custom AAGUID values and default anonymous AAGUID behavior

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[dimitribouniol]

This looks great, thanks!