Semantic Reranking: Refactors RerankResult.Document to return string type (#5528)

# Pull Request Template

## Description

This pull request updates the handling of the `Document` property in the
`RerankScore` class and its deserialization logic to consistently use a
`string` type instead of a generic `object`. This change simplifies the
type system and ensures that document content or identifiers are always
represented as strings which is returned by the service.

Type consistency and deserialization improvements:

* Changed the `Document` property in the `RerankScore` class from
`object` to `string`, and updated the constructor accordingly to require
a `string` document.
[[1]](diffhunk://#diff-8278775c5227f8e0f3aa61d4b0a96434387143cde3ea6a4e1d4445362a559530L21-R21)
[[2]](diffhunk://#diff-8278775c5227f8e0f3aa61d4b0a96434387143cde3ea6a4e1d4445362a559530L39-R39)
* Updated the deserialization logic in `DeserializeSemanticRerankResult`
to always store the document as a string, either by using the raw JSON
text for objects or the string value directly, ensuring type consistency
throughout the codebase.

## Type of change

Please delete options that are not relevant.

- [] Bug fix (non-breaking change which fixes an issue)

## Closing issues

To automatically close an issue: closes #IssueNumber

Author: NaluTripician

Microsoft.Azure.Cosmos/src/Inference/RerankScore.cs

@@ -18,7 +18,7 @@ class RerankScore
         /// <summary>
         /// Gets the document content or identifier that was reranked.
         /// </summary>
-        public object Document { get; }
+        public string Document { get; }
 
         /// <summary>
         /// Gets the score assigned to the document after reranking.
@@ -36,7 +36,7 @@ class RerankScore
         /// <param name="document">The document content or identifier.</param>
         /// <param name="score">The reranked score for the document.</param>
         /// <param name="index">The original index of the document.</param>
-        public RerankScore(object document, double score, int index)
+        public RerankScore(string document, double score, int index)
         {
             this.Document = document;
             this.Score = score;

Microsoft.Azure.Cosmos/src/Inference/SemanticRerankResult.cs

@@ -83,17 +83,19 @@ internal static async Task<SemanticRerankResult> DeserializeSemanticRerankResult
                     {
                         foreach (JsonElement item in scoresElement.EnumerateArray())
                         {
-                            object document = null;
+                            string document = string.Empty;
                             if (item.TryGetProperty("document", out JsonElement docElement))
                             {
                                 // Try to deserialize as an object
                                 switch (docElement.ValueKind)
                                 {
                                     case JsonValueKind.Object:
-                                        document = JsonSerializer.Deserialize<Dictionary<string, object>>(docElement.GetRawText());
+                                        document = docElement.GetRawText();
                                         break;
-                                    case JsonValueKind.Null:
-                                        document = null;
+                                    case JsonValueKind.String:
+                                        document = docElement.GetString();
+                                        break;
+                                    default:
                                         break;
                                 }
                             }

Microsoft.Azure.Cosmos/tests/Microsoft.Azure.Cosmos.Tests/Contracts/DotNetPreviewSDKAPI.net6.json

@@ -1452,22 +1452,22 @@
           "Attributes": [],
           "MethodInfo": "Int32 Index;CanRead:True;CanWrite:False;Int32 get_Index();IsAbstract:False;IsStatic:False;IsVirtual:False;IsGenericMethod:False;IsConstructor:False;IsFinal:False;"
         },
-        "System.Object Document": {
+        "System.String Document": {
           "Type": "Property",
           "Attributes": [],
-          "MethodInfo": "System.Object Document;CanRead:True;CanWrite:False;System.Object get_Document();IsAbstract:False;IsStatic:False;IsVirtual:False;IsGenericMethod:False;IsConstructor:False;IsFinal:False;"
+          "MethodInfo": "System.String Document;CanRead:True;CanWrite:False;System.String get_Document();IsAbstract:False;IsStatic:False;IsVirtual:False;IsGenericMethod:False;IsConstructor:False;IsFinal:False;"
         },
-        "System.Object get_Document()[System.Runtime.CompilerServices.CompilerGeneratedAttribute()]": {
+        "System.String get_Document()[System.Runtime.CompilerServices.CompilerGeneratedAttribute()]": {
           "Type": "Method",
           "Attributes": [
             "CompilerGeneratedAttribute"
           ],
-          "MethodInfo": "System.Object get_Document();IsAbstract:False;IsStatic:False;IsVirtual:False;IsGenericMethod:False;IsConstructor:False;IsFinal:False;"
+          "MethodInfo": "System.String get_Document();IsAbstract:False;IsStatic:False;IsVirtual:False;IsGenericMethod:False;IsConstructor:False;IsFinal:False;"
         },
-        "Void .ctor(System.Object, Double, Int32)": {
+        "Void .ctor(System.String, Double, Int32)": {
           "Type": "Constructor",
           "Attributes": [],
-          "MethodInfo": "Void .ctor(System.Object, Double, Int32)"
+          "MethodInfo": "Void .ctor(System.String, Double, Int32)"
         }
       },
       "NestedTypes": {}