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Clouds: Authenticate on Dropbox service on consequent connections
Unforutnately Dropbox doesn't support access token refreshing technology). Instead they offer access tokens with quite long lifespan (currently it's 1 year).
As soon as the access token is saved, there's no need to ask the user about authorization in browser each time the application is started. Instead you can use the saved access token to access the user account on the server.
Also we recommend to keep access token expiration date (see TElDropboxDataStorage.AccessTokenExpiration property) to know, when the token expires and it is time to ask the user for re-authentication. However, this is not required, because the access token can be used until the server returns authentication error. Once the error is returned, you will need to perform authentication as if it were the first-time authentication.
So to use the saved access token you need to