Update to dotnet 9.0, add user roles, MatchStats and OpenApi/Scalar in dev

LaDOSE.Src/LaDOSE.Service/Interface/IStatisticsService.cs

@@ -0,0 +1,16 @@
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using LaDOSE.Entity;
+
+namespace LaDOSE.Business.Interface
+{
+    public interface IStatisticsService
+    {
+        /// <summary>
+        /// Aggregate the persisted sets of the given Events into per-player records,
+        /// head-to-head records and a coverage report.
+        /// A null or empty id list yields a well-formed, zeroed <see cref="MatchStats"/>.
+        /// </summary>
+        Task<MatchStats> GetMatchStats(List<int> eventIds);
+    }
+}