Fix #3625: add the clear logs function.

Oqtane.Client/Services/Interfaces/ILogService.cs

@@ -29,6 +29,13 @@ namespace Oqtane.Services
         /// <returns></returns>
         Task<Log> GetLogAsync(int logId);
 
+        /// <summary>
+        /// Clear the entire logs of the given site.
+        /// </summary>
+        /// <param name="siteId"></param>
+        /// <returns></returns>
+        Task ClearLogsAsync(int siteId);
+
         /// <summary>
         /// Creates a new log entry
         /// </summary>