fix: Improved passwordless docs (#8363)

* Add swift content for WebAuthn Passkeys

* Add managing credentials blurb

* Add more details about setting up passkeys for Android

* Improve passwordless docs for Android

* Update managing credentials blurb

* Fix spelling check failures

* Add Swift code samples for password and for selecting preferred challenge

Author: mattcreaser

src/pages/[platform]/build-a-backend/auth/concepts/passwordless/index.mdx

@@ -42,7 +42,7 @@ Passwordless authentication removes the security risks and user friction associa
 
 </Callout>
 
-Learn how to implement passwordless sign-in flows by [overriding the Cognito UserPool to enable the sign-in methods below](/[platform]/build-a-backend/auth/modify-resources-with-cdk/#override-cognito-userpool-to-enable-passwordless-sign-in-methods).
+Learn how to enable passwordless sign-in flows by [overriding the Cognito UserPool to enable the sign-in methods below](/[platform]/build-a-backend/auth/modify-resources-with-cdk/#override-cognito-userpool-to-enable-passwordless-sign-in-methods).
 
 {/* need a section about what a "preferred" factor is */}
 
@@ -131,7 +131,17 @@ WebAuthn uses biometrics or security keys for authentication, leveraging device-
 </InlineFilter>
 <InlineFilter filters={["android"]}>
 
-{/*  */}
+You can read more about how passkeys work in the [Android developer docs](https://developer.android.com/design/ui/mobile/guides/patterns/passkeys).
+
+<Callout warning>
+Registering a passkey is supported on Android 9 (API level 28) and above.
+</Callout>
+
+Using passkeys with Amplify requires following these steps:
+
+1. Deploy a Digital Asset Links file to your website granting the `get_login_creds` permission to your application. See the [Credential Manager documentation](https://developer.android.com/identity/sign-in/credential-manager#add-support-dal) for more details about this file.
+1. [Configure your Amazon Cognito user pool](/[platform]/build-a-backend/auth/modify-resources-with-cdk/#override-cognito-userpool-to-enable-passwordless-sign-in-methods) with `WEB_AUTHN` as an allowed first factor, and specify your website domain as the `WebAuthnRelyingPartyID`.
+1. Use the Amplify Android APIs to first [register a passkey](/[platform]/build-a-backend/auth/manage-users/manage-webauthn-credentials/#associate-webauthn-credentials) and then to [sign in with WebAuthn](/[platform]/build-a-backend/auth/connect-your-frontend/sign-in/#webauthn-passkeys).
 
 </InlineFilter>
 <InlineFilter filters={["swift"]}>
@@ -144,6 +154,6 @@ WebAuthn uses biometrics or security keys for authentication, leveraging device-
 
 ### Managing credentials
 
-{/* quick blurb then segue over to "manage WebAuthn credentials" page */}
+Passwordless authentication with WebAuthn requires associating one or more credentials with the user's Amazon Cognito account. Amplify provides APIs that integrate with each platform's local authenticator to easily create, view, and delete these credential associations.
 
 [Learn more about managing WebAuthn credentials](/[platform]/build-a-backend/auth/manage-users/manage-webauthn-credentials).