Passkeys implementation in Swift

I was trying to implement passkeys in an app. I have a doubt on this. While logging in to the application, the application shows a bunch of users who were registered earlier on that device. So when the user tries to login with the passkey in that bunch of passkeys in the device, so as a developer how do I know which passkey is used (So that I can retrieve the username for that specific passkeys)

When your server receives and decodes the assertion response, one of the fields is the credentialID. That identifies the specific passkey that was used, and can be mapped to a specific user account on the backend.

Passkeys implementation in Swift
 
 
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