Add support for $ref lookups in ResponseSchema

https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.0.md#response-object
https://readme.readme.io/v2.0/discuss/5c17c3fe0252e4030b7264a9

Author: domharrington

packages/api-explorer/__tests__/ResponseSchema.test.jsx

@@ -149,7 +149,45 @@ test('should contain ResponseSchemaBody element if $ref exist for "application/x
   };
 
   const responseSchema = shallow(<ResponseSchema {...testProps} />);
-  expect(responseSchema.text()).toContain('ResponseSchemaBody');
+  expect(responseSchema.find('ResponseSchemaBody').length).toBe(1);
+});
+
+test('should allow $ref lookup at the responses object level', () => {
+  const testOas = new Oas({
+    components: {
+      responses: {
+        Response: {
+          content: {
+            'application/json': {
+              schema: {
+                type: 'string',
+              },
+            },
+          },
+        },
+      },
+    },
+    paths: {
+      '/ref-responses': {
+        get: {
+          responses: {
+            200: {
+              $ref: '#/components/responses/Response',
+            },
+          },
+        },
+      },
+    },
+  });
+
+  const responseSchema = shallow(
+    <ResponseSchema
+      {...props}
+      oas={testOas}
+      operation={testOas.operation('/ref-responses', 'get')}
+    />,
+  );
+  expect(responseSchema.find('ResponseSchemaBody').length).toBe(1);
 });
 
 test('should change selectedStatus in component', () => {

packages/api-explorer/src/ResponseSchema.jsx

@@ -19,12 +19,11 @@ class ResponseSchema extends React.Component {
   }
 
   getSchema(operation) {
-    const content = this.getContent(operation);
+    const oas = this.props.oas;
+    const content = this.getContent(operation, oas);
 
     if (!content) return null;
 
-    const oas = this.props.oas;
-
     const firstContentType = Object.keys(content)[0];
 
     if (
@@ -42,14 +41,14 @@ class ResponseSchema extends React.Component {
     return null;
   }
 
-  getContent(operation) {
+  getContent(operation, oas) {
     const status = this.state.selectedStatus;
-    return (
-      operation &&
-      operation.responses &&
-      operation.responses[status] &&
-      operation.responses[status].content
-    );
+    const response = operation && operation.responses && operation.responses[status];
+
+    if (!response) return false;
+
+    if (response.$ref) return findSchemaDefinition(response.$ref, oas).content;
+    return response.content;
   }
 
   changeHandler(e) {