[client] Force interactive login when extending the auth session

A session extend must be answered from the account the peer is registered
under. With a silent PKCE flow (DisablePromptLogin or max_age=0) the IdP
answers from whatever session it already holds, which need not be the
peer's account when several are signed in; the token then fails the
user match in ExtendAuthSession with no way to pick another account.

Mark the PKCE flow request as a session extend so the management server
can force prompt=login for it, overriding the configured silent flow.

client/ios/NetBirdSDK/client.go

@@ -429,7 +429,7 @@ func (c *Client) LoginForMobile() string {
 		return fmt.Sprintf("failed to load config: %v", err)
 	}
 
-	oAuthFlow, err := auth.NewOAuthFlow(ctx, cfg, false, false, "")
+	oAuthFlow, err := auth.NewOAuthFlow(ctx, cfg, false, false, "", false)
 	if err != nil {
 		return err.Error()
 	}

client/ios/NetBirdSDK/login.go

@@ -323,7 +323,7 @@ func (a *Auth) login(urlOpener URLOpener, forceDeviceAuth bool, deviceName strin
 const authInfoRequestTimeout = 30 * time.Second
 
 func (a *Auth) foregroundGetTokenInfo(authClient *auth.Auth, urlOpener URLOpener, forceDeviceAuth bool) (*auth.TokenInfo, error) {
-	oAuthFlow, err := authClient.GetOAuthFlow(a.ctx, forceDeviceAuth)
+	oAuthFlow, err := authClient.GetOAuthFlow(a.ctx, forceDeviceAuth, false)
 	if err != nil {
 		return nil, fmt.Errorf("failed to get OAuth flow: %v", err)
 	}