Update DI and serialization logic for GraphQL client

Replaces singleton registration in DI with keyed singleton for better service resolution. Updates `JsonSerializerOptions` initialization to simplified syntax and removes unnecessary properties. Refines error-handling logic in query execution and adjusts template to support keyed service injection.

Author: magahl-swegon

src/Linq2GraphQL.Client/GraphClient.cs

@@ -22,10 +22,10 @@ public GraphClient(HttpClient httpClient, IOptions<GraphClientOptions> options,
 
         HttpClient = httpClient;
 
-        SerializerOptions = new JsonSerializerOptions
+        SerializerOptions = new()
         {
             DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
-            WriteIndented = true
+            Converters = {  }
         };
 
         SubscriptionUrl = GetSubscriptionUrl();

src/Linq2GraphQL.Client/QueryExecutor.cs

@@ -40,8 +40,8 @@ public T ProcessResponse(string con, string name, string query)
             throw new GraphQueryExecutionException(errors, query);
         }
 
-        var hasData = document.RootElement.TryGetProperty(dataPathPropertyName, out var dataElement);
-        var hasResult = dataElement.TryGetProperty(name, out var resultElement);
+        document.RootElement.TryGetProperty(dataPathPropertyName, out var dataElement);
+        dataElement.TryGetProperty(name, out var resultElement);
 
         if (resultElement.ValueKind == JsonValueKind.Null)
         {

src/Linq2GraphQL.Generator/Templates/Client/ClientTemplate.tt

@@ -9,7 +9,7 @@ namespace <#= namespaceName #>;
 
 public class <#= name #>
 {
-    public <#= name #>(HttpClient httpClient, IOptions<GraphClientOptions> options, IServiceProvider provider)
+    public <#= name #>(HttpClient httpClient, [FromKeyedServices("<#= name #>")]IOptions<GraphClientOptions> options, IServiceProvider provider)
     {
         var client = new GraphClient(httpClient, options, provider);
 <# if (includeQuery) { #>

test/Linq2GraphQL.TestClient/Generated/Client/SampleClientExtensions.cs

@@ -26,7 +26,7 @@ private static IGraphClientBuilder<SampleClient> GraphClientBuilder(IServiceColl
         GraphClientOptions graphClientOptions)
     {
         var opts = Options.Create(graphClientOptions);
-        services.AddSingleton(opts);
+        services.AddKeyedSingleton(opts, ClientName);
         services.AddMemoryCache();        
         return new ClientBuilder<SampleClient>(ClientName, services);
     }