Add Joining table object to link users to groups.

#59

DataCenter_Windows/WindowsDataCenter/SQLiteRepository/UserGroupJoinDb.cs

@@ -0,0 +1,12 @@
+using SQLite.Net.Attributes;
+
+namespace SQLiteRepository
+{
+    internal class UserGroupJoinDb
+    {
+        [PrimaryKey, AutoIncrement]
+        public int JoinPKId { get; set; }
+        public int UserId_FK { get; set; }
+        public int GroupId_FK { get; set; }
+    }
+}