Reference unions from the fields of wired types too, since a union can lead back to the wired type

Author: oryan-block

src/main/kotlin/graphql/kickstart/tools/directive/DirectiveWiringHelper.kt

@@ -77,7 +77,7 @@ internal class DirectiveWiringHelper(
             is GraphQLNonNull -> GraphQLNonNull.nonNull(of(type.wrappedType))
             is GraphQLList -> GraphQLList.list(of(type.wrappedType))
             // only these can lead back to the wired type. Scalars stay, since a reference only finds a scalar another field uses
-            is GraphQLFieldsContainer, is GraphQLInputObjectType ->
+            is GraphQLFieldsContainer, is GraphQLUnionType, is GraphQLInputObjectType ->
                 if (schema.typeMap[type.name] === type) GraphQLTypeReference.typeRef(type.name) else built.getOrPut(type) { inFields(type) }
             else -> type
         }

src/test/kotlin/graphql/kickstart/tools/DirectiveTest.kt

@@ -273,8 +273,11 @@ class DirectiveTest {
                     age: Int
                     friend: Person @required
                     best: Person @wrap
+                    someone: Someone
                 }
 
+                union Someone = Person
+
                 input PersonFilter {
                     name: String
                     parent: PersonFilter @many
@@ -880,6 +883,7 @@ class DirectiveTest {
     class Person(val name: String, val age: Int = 1) {
         val friend: Person get() = this
         val best: Person get() = this
+        val someone: Person get() = this
     }
 
     data class PersonFilter(