Added OneOf support to Mutable (#8648)

Author: glen-84

src/HotChocolate/Mutable/src/Types.Mutable/BuiltIns/BuiltIns.cs

@@ -105,6 +105,16 @@ public static SpecifiedByMutableDirectiveDefinition Create(MutableSchemaDefiniti
         }
     }
 
+    public static class OneOf
+    {
+        public const string Name = "oneOf";
+
+        public static OneOfMutableDirectiveDefinition Create()
+        {
+            return new OneOfMutableDirectiveDefinition();
+        }
+    }
+
     public static bool IsBuiltInScalar(string name)
         => name switch
         {
@@ -123,6 +133,7 @@ public static bool IsBuiltInDirective(string name)
             Skip.Name => true,
             Deprecated.Name => true,
             SpecifiedBy.Name => true,
+            OneOf.Name => true,
             _ => false
         };
 }

src/HotChocolate/Mutable/src/Types.Mutable/BuiltIns/OneOfMutableDirectiveDefinition.cs

@@ -0,0 +1,11 @@
+namespace HotChocolate.Types.Mutable;
+
+public sealed class OneOfMutableDirectiveDefinition : MutableDirectiveDefinition
+{
+    internal OneOfMutableDirectiveDefinition()
+        : base(BuiltIns.OneOf.Name)
+    {
+        IsSpecDirective = true;
+        Locations = DirectiveLocation.InputObject;
+    }
+}

src/HotChocolate/Mutable/src/Types.Mutable/Serialization/SchemaParser.cs

@@ -709,6 +709,10 @@ private static void BuildDirectiveCollection(
                 {
                     directiveType = BuiltIns.Deprecated.Create(schema);
                 }
+                else if (directiveNode.Name.Value == BuiltIns.OneOf.Name)
+                {
+                    directiveType = BuiltIns.OneOf.Create();
+                }
                 else if (directiveNode.Name.Value == BuiltIns.SpecifiedBy.Name)
                 {
                     directiveType = BuiltIns.SpecifiedBy.Create(schema);