Custom scopes cannot be added when refreshing tokens

[harmjanr]

I have setup some custom scopes: For example, I added the client id to the scopes to use access tokens, which is required for the web implementation of my project.

In client_authentication.dart, the providedScopes param available in the getAllTokens method. However, this param is missing in refreshTokens. Because of this, the response of refreshing the tokens does not contain an access_token, but only an id_token and a refresh_token.

[harmjanr]

I created a PR to support this: #48