Updated IntrospectionFormatter to set default deprecation reason (#8752)

Author: glen-84

src/HotChocolate/Utilities/src/Utilities.Introspection/IntrospectionFormatter.cs

@@ -317,8 +317,16 @@ private static IReadOnlyList<NamedTypeNode> CreateNamedTypeRefs(
     }
 
     private static IReadOnlyList<DirectiveNode> CreateDeprecatedDirective(
-        bool isDeprecated, string deprecationReason)
+        bool isDeprecated,
+        string deprecationReason)
     {
+        const string defaultReason = "No longer supported.";
+
+        if (string.IsNullOrEmpty(deprecationReason))
+        {
+            deprecationReason = defaultReason;
+        }
+
         if (isDeprecated)
         {
             return new List<DirectiveNode>

src/HotChocolate/Utilities/test/Utilities.Introspection.Tests/IntrospectionFormatterTests.cs

@@ -32,4 +32,18 @@ public void DeserializeIntrospectionWithIntDefaultValues()
         // assert
         schema.ToString(true).MatchSnapshot();
     }
+
+    [Fact]
+    public void DeserializeIntrospectionWithNullDeprecationReason()
+    {
+        // arrange
+        var json = FileResource.Open("IntrospectionWithNullDeprecationReason.json");
+        var result = JsonSerializer.Deserialize<IntrospectionResult>(json, SerializerOptions);
+
+        // act
+        var schema = IntrospectionFormatter.Format(result!);
+
+        // assert
+        schema.ToString(true).MatchSnapshot();
+    }
 }