Extended OAuthHelper to work better with the Dropbox OAuth implementation

Duplicati/Library/Backend/OAuthHelper/OAuthHelper.cs

@@ -25,7 +25,7 @@ namespace Duplicati.Library
     {
         private string m_token;
         private string m_authid;
-        private DateTime m_tokenExpires = DateTime.UtcNow;
+		private DateTime m_tokenExpires = DateTime.UtcNow;
 
         private static string _override_server = null;
 
@@ -45,7 +45,14 @@ namespace Duplicati.Library
             return string.Format(addr.ToString(), modulename); 
         }
 
+		/// <summary>
+		/// Set to true to automatically add the Authorization header to requets
+		/// </summary>
         public bool AutoAuthHeader { get; set; }
+		/// <summary>
+		/// Set to true if the provider does not use refresh tokens, but only access tokens
+		/// </summary>
+		public bool AccessTokenOnly { get; set; }
 
         public OAuthHelper(string authid, string servicename, string useragent = null)
             : base(useragent)
@@ -78,6 +85,9 @@ namespace Duplicati.Library
         {
             get
             {
+				if (AccessTokenOnly)
+					return m_authid;
+
                 if (m_token == null || m_tokenExpires < DateTime.UtcNow)
                 {
                     var retries = 0;
@@ -132,6 +142,19 @@ namespace Duplicati.Library
             }
         }
 
+		public void ThrowOverQuotaError()
+		{
+			throw new Exception(Strings.OAuthHelper.OverQuotaError);
+		}
+
+		public void ThrowAuthException(string msg, Exception ex)
+		{
+			if (ex == null)
+				throw new Exception(Strings.OAuthHelper.AuthorizationFailure(msg, OAuthLoginUrl));
+			else
+				throw new Exception(Strings.OAuthHelper.AuthorizationFailure(msg, OAuthLoginUrl), ex);
+		}
+
 
 
         private class OAuth_Service_Response