Revoke the access token

When the token is not required anymore, the access_token should be revoked.

Currently, the Thinktecture library does not provide a method to revoke the token.

This is an example:

private void _revokeToken(string token, string tokenType)
{
var client = new HttpClient();
client.SetBasicAuthentication(ClientId, ClientSecret);
var postBody = new Dictionary<string, string>
{
{ "token", token },
{ "token_type_hint", tokenType }
};
var result = client.PostAsync(OAuth2TokenRevocationEndpoint, new FormUrlEncodedContent(postBody)).}

To revoke the access token, use this call:

_revokeToken(this.AccessTokenTextBox.Text, OAuth2Constants.AccessToken);