Polls persist restarts now.

NadekoBot.Core/Services/Database/Models/Poll.cs

@@ -3,15 +3,16 @@ using System.Collections.Generic;
 
 namespace NadekoBot.Core.Services.Database.Models
 {
-    public class Poll
+    public class Poll : DbEntity
     {
         public ulong GuildId { get; set; }
+        public ulong ChannelId { get; set; }
         public string Question { get; set; }
         public IndexedCollection<PollAnswer> Answers { get; set; }
-        public HashSet<PollVote> Votes { get; set; }
+        public HashSet<PollVote> Votes { get; set; } = new HashSet<PollVote>();
     }
 
-    public class PollAnswer : IIndexed
+    public class PollAnswer : DbEntity, IIndexed
     {
         public int Index { get; set; }
         public string Text { get; set; }

NadekoBot.Core/Services/Database/Models/PollVote.cs

@@ -1,13 +1,20 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace NadekoBot.Core.Services.Database.Models
+namespace NadekoBot.Core.Services.Database.Models
 {
-    public class PollVote
+    public class PollVote : DbEntity
     {
-        
+        public ulong UserId { get; set; }
+        public int VoteIndex { get; set; }
+
+        public override int GetHashCode()
+        {
+            return UserId.GetHashCode();
+        }
+
+        public override bool Equals(object obj)
+        {
+            return obj is PollVote p
+                ? p.UserId == UserId
+                : false;
+        }
     }
 }