Add variable question distractor pools

api/QuestionsApi/Models/AnswerStatistics.cs

@@ -7,7 +7,8 @@ public sealed class QuestionAttemptCounter
     public string QuestionExternalId { get; set; } = "";
     public int Bucket { get; set; }
     public string ChoiceId { get; set; } = "";
-    public long Count { get; set; }
+    public long SelectionCount { get; set; }
+    public long PresentationCount { get; set; }
     public DateTime UpdatedUtc { get; set; } = DateTime.UtcNow;
 }
 
@@ -15,14 +16,16 @@ public sealed class QuestionAttemptCounterTotal
 {
     [BsonId]
     public QuestionChoiceCounterKey Key { get; set; } = new();
-    public long Count { get; set; }
+    public long SelectionCount { get; set; }
+    public long PresentationCount { get; set; }
 }
 
 public sealed class QuestionAttemptCounterAggregate
 {
     [BsonId]
     public QuestionChoiceBucketKey Key { get; set; } = new();
-    public long Count { get; set; }
+    public long SelectionCount { get; set; }
+    public long PresentationCount { get; set; }
 }
 
 public sealed class QuestionChoiceBucketKey
@@ -41,9 +44,18 @@ public sealed class QuestionChoiceCounterKey
 public sealed class AnswerStatisticsState
 {
     [BsonId]
-    public string Id { get; set; } = "answer-statistics-v1";
+    public string Id { get; set; } = "answer-statistics-v2";
     public bool Completed { get; set; }
     public string LeaseOwner { get; set; } = "";
     public DateTime LeaseUntilUtc { get; set; }
     public DateTime UpdatedUtc { get; set; } = DateTime.UtcNow;
+    public DateTime CutoverUtc { get; set; }
+}
+
+public sealed class QuestionPresentationBaseline
+{
+    [BsonId]
+    public string QuestionExternalId { get; set; } = "";
+    public List<string> ChoiceIds { get; set; } = [];
+    public DateTime CreatedUtc { get; set; } = DateTime.UtcNow;
 }