Mostly backend models stuff

Changed some models, did some work on database, created a class diagram.

KTUSAPS.Data/SAPSDataContext.cs

@@ -1,4 +1,5 @@
-using Microsoft.EntityFrameworkCore;
+using KTUSAPS.Data.Model;
+using Microsoft.EntityFrameworkCore;
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -13,7 +14,8 @@ namespace KTUSAPS.Data
         public SAPSDataContext(DbContextOptions options) : base(options) { }
         protected override void OnModelCreating(ModelBuilder modelBuilder)
         {
-
+            modelBuilder.Entity<Vote>()
+                .HasKey(v => new { v.UserId, v.ProblemId });
         }
 
         protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
@@ -24,6 +26,11 @@ namespace KTUSAPS.Data
             }
         }
 
+        public DbSet<Issue> Issues { get; set; }
+        public DbSet<PublishedFeedback> PublishedFeedbacks { get; set; }
+        public DbSet<PublishedProblem> PublishedProblems { get; set; }
+        public DbSet<Solution> Solutions { get; set; }
+        public DbSet<Vote> Votes { get; set; }
 
     }
 }