Use EFCore to store preferences (#506)

* Use EFcore to store preferences

* Fixed nullabilty warnings

Content.Server.Database/Model.cs

@@ -0,0 +1,51 @@
+using System.Collections.Generic;
+using Microsoft.EntityFrameworkCore;
+
+namespace Content.Server.Database
+{
+    public class PreferencesDbContext : DbContext
+    {
+        // This is used by the "dotnet ef" CLI tool.
+        public PreferencesDbContext() :
+            base(new DbContextOptionsBuilder().UseSqlite("Data Source=:memory:").Options)
+        {
+        }
+
+        public PreferencesDbContext(DbContextOptions<PreferencesDbContext> options) : base(options)
+        {
+        }
+
+        public DbSet<Prefs> Preferences { get; set; } = null!;
+
+        protected override void OnModelCreating(ModelBuilder modelBuilder)
+        {
+            modelBuilder.Entity<Prefs>()
+                .HasIndex(p => p.Username)
+                .IsUnique();
+        }
+    }
+
+    public class Prefs
+    {
+        public int PrefsId { get; set; }
+        public string Username { get; set; } = null!;
+        public int SelectedCharacterSlot { get; set; }
+        public List<HumanoidProfile> HumanoidProfiles { get; } = new List<HumanoidProfile>();
+    }
+
+    public class HumanoidProfile
+    {
+        public int HumanoidProfileId { get; set; }
+        public int Slot { get; set; }
+        public string SlotName { get; set; } = null!;
+        public string CharacterName { get; set; } = null!;
+        public int Age { get; set; }
+        public string Sex { get; set; } = null!;
+        public string HairName { get; set; } = null!;
+        public string HairColor { get; set; } = null!;
+        public string FacialHairName { get; set; } = null!;
+        public string FacialHairColor { get; set; } = null!;
+        public string EyeColor { get; set; } = null!;
+        public string SkinColor { get; set; } = null!;
+    }
+}