Passkeys improvements (#10318)

Refactors the Passkey implementation to include more checks and a structure that is more aligned with the official specification.
Notable changes:
- _BrowserService_ no longer does the checks by itself. A new class _BrowserPasskeysClient_ constructs the relevant objects, acting as a client. _BrowserService_ only acts as a bridge between the client and _BrowserPasskeys_ (authenticator) and calls the relevant popups for user interaction.
- A new helper class _PasskeyUtils_ includes the actual checks and parses the objects.
- _BrowserPasskeys_ is pretty much intact, but some functions have been moved to PasskeyUtils.
- Fixes Ed25519 encoding in _BrowserCBOR_.
- Adds new error messages.
- User confirmation for Passkey retrieval is also asked even if `discouraged` is used. This goes against the specification, but currently there's no other way to verify the user.
- `cross-platform` is also accepted for compatibility. This could be removed if there's a potential issue with it.
- Extension data is now handled correctly during Authentication.
- Allowed and excluded credentials are now handled correctly.
- `KPEX_PASSKEY_GENERATED_USER_ID` is renamed to `KPEX_PASSKEY_CREDENTIAL_ID`
- Adds a new option "Allow localhost with Passkeys" to Browser Integration -> Advanced tab. By default it's not allowed to access HTTP sites, but `http://localhost` can be allowed for debugging and testing purposes for local servers.
- Add tag `Passkey` to a Passkey entry, or an entry with an imported Passkey.

Fixes #10287.

src/core/Config.cpp

@@ -1,5 +1,5 @@
 /*
- *  Copyright (C) 2020 KeePassXC Team <team@keepassxc.org>
+ *  Copyright (C) 2024 KeePassXC Team <team@keepassxc.org>
  *  Copyright (C) 2011 Felix Geyer <debfx@fobos.de>
  *
  *  This program is free software: you can redistribute it and/or modify
@@ -167,6 +167,7 @@ static const QHash<Config::ConfigKey, ConfigDirective> configStrings = {
     {Config::Browser_UseCustomBrowser, {QS("Browser/UseCustomBrowser"), Local, false}},
     {Config::Browser_CustomBrowserType, {QS("Browser/CustomBrowserType"), Local, -1}},
     {Config::Browser_CustomBrowserLocation, {QS("Browser/CustomBrowserLocation"), Local, {}}},
+    {Config::Browser_AllowLocalhostWithPasskeys, {QS("Browser/Browser_AllowLocalhostWithPasskeys"), Roaming, false}},
 #ifdef QT_DEBUG
     {Config::Browser_CustomExtensionId, {QS("Browser/CustomExtensionId"), Local, {}}},
 #endif