GraphQL: Support required fields on output type (#6279)

* Handle required fields

* Fix output fields

spec/ParseGraphQLServer.spec.js

@@ -1886,6 +1886,32 @@ describe('ParseGraphQLServer', () => {
           expect(
             __type.inputFields.find(o => o.name === 'doors').type.kind
           ).toEqual('NON_NULL');
+
+          const {
+            data: { __type: __type2 },
+          } = await apolloClient.query({
+            query: gql`
+              query requiredFields {
+                __type(name: "SuperCar") {
+                  fields {
+                    name
+                    type {
+                      kind
+                    }
+                  }
+                }
+              }
+            `,
+          });
+          expect(
+            __type2.fields.find(o => o.name === 'price').type.kind
+          ).toEqual('SCALAR');
+          expect(
+            __type2.fields.find(o => o.name === 'engine').type.kind
+          ).toEqual('NON_NULL');
+          expect(
+            __type2.fields.find(o => o.name === 'doors').type.kind
+          ).toEqual('NON_NULL');
         });
 
         it('should only allow the supplied output fields for a class', async () => {