chore: rename MVI search hit Distance property to Score (#514)

To align with the scoreThreshold option in search, and for
clarity in that the search hits are not ordered by distance (which
is lower or better), but by score (which could be higher or better,
or a blend of multiple things), we rename the distance property to
score.

src/Momento.Sdk/Responses/Vector/SearchHit.cs

@@ -5,7 +5,7 @@ namespace Momento.Sdk.Responses.Vector;
 using System.Collections.Generic;
 
 /// <summary>
-/// A hit from a vector search. Contains the ID of the vector, the distance from the query vector,
+/// A hit from a vector search. Contains the ID of the vector, the search score,
 /// and any requested metadata.
 /// </summary>
 public class SearchHit
@@ -16,9 +16,9 @@ public class SearchHit
     public string Id { get; }
 
     /// <summary>
-    /// The distance from the query vector.
+    /// The similarity to the query vector.
     /// </summary>
-    public double Distance { get; }
+    public double Score { get; }
 
     /// <summary>
     /// Requested metadata associated with the hit.
@@ -29,37 +29,38 @@ public class SearchHit
     /// Constructs a SearchHit with no metadata.
     /// </summary>
     /// <param name="id">The ID of the hit.</param>
-    /// <param name="distance">The distance from the query vector.</param>
-    public SearchHit(string id, double distance)
+    /// <param name="score">The similarity to the query vector.</param>
+    public SearchHit(string id, double score)
     {
         Id = id;
-        Distance = distance;
+        Score = score;
         Metadata = new Dictionary<string, MetadataValue>();
     }
 
     /// <summary>
     /// Constructs a SearchHit.
     /// </summary>
     /// <param name="id">The ID of the hit.</param>
-    /// <param name="distance">The distance from the query vector.</param>
+    /// <param name="score">The similarity to the query vector.</param>
     /// <param name="metadata">Requested metadata associated with the hit</param>
-    public SearchHit(string id, double distance, Dictionary<string, MetadataValue> metadata)
+    public SearchHit(string id, double score, Dictionary<string, MetadataValue> metadata)
     {
         Id = id;
-        Distance = distance;
+        Score = score;
         Metadata = metadata;
     }
 
     /// <inheritdoc />
     public override bool Equals(object obj)
     {
         if (ReferenceEquals(this, obj)) return true;
+        // ReSharper disable once ConditionIsAlwaysTrueOrFalseAccordingToNullableAPIContract
         if (obj is null || GetType() != obj.GetType()) return false;
 
         var other = (SearchHit)obj;
 
         // ReSharper disable once CompareOfFloatsByEqualityOperator
-        if (Id != other.Id || Distance != other.Distance) return false;
+        if (Id != other.Id || Score != other.Score) return false;
 
         // Compare Metadata dictionaries
         if (Metadata.Count != other.Metadata.Count) return false;
@@ -81,7 +82,7 @@ public override int GetHashCode()
             var hash = 17;
 
             hash = hash * 23 + Id.GetHashCode();
-            hash = hash * 23 + Distance.GetHashCode();
+            hash = hash * 23 + Score.GetHashCode();
 
             foreach (var pair in Metadata)
             {

src/Momento.Sdk/Responses/Vector/SearchResponse.cs

@@ -49,7 +49,7 @@ public Success(List<SearchHit> hits)
         /// <inheritdoc />
         public override string ToString()
         {
-            var displayedHits = Hits.Take(5).Select(hit => $"{hit.Id} ({hit.Distance})");
+            var displayedHits = Hits.Take(5).Select(hit => $"{hit.Id} ({hit.Score})");
             return $"{base.ToString()}: {string.Join(", ", displayedHits)}...";
         }