Fixes response_validator to handle 3.0 responses and validate against the schema.

JSON::Validator already handles anyOf oneOf schema definitions, so those can be passed in and validation errors are returned properly

test-app/app/controllers/blogs_controller.rb

@@ -15,7 +15,6 @@ class BlogsController < ApplicationController
     # request body definition for 3.0
     blog_params = params.require(:blog).permit(:title, :content, :headline, :text)
 
-
     @blog = Blog.create(blog_params)
     respond_with @blog
   end

test-app/spec/integration/blogs_spec.rb

@@ -74,7 +74,7 @@ describe 'Blogs API', type: :request, swagger_doc: 'v1/swagger.json' do
       let(:flexible_blog) { { blog: { headline: 'my headline', text: 'my text' } } }
 
       response '201', 'flexible blog created' do
-        schema '$ref' => '#/components/schemas/blog'
+        schema :oneOf => [{'$ref' => '#/components/schemas/blog'},{'$ref' => '#/components/schemas/flexible_blog'}]
         run_test!
       end
     end
@@ -120,7 +120,7 @@ describe 'Blogs API', type: :request, swagger_doc: 'v1/swagger.json' do
     end
   end
 
-  
+
   path '/blogs/{id}/upload' do
     let(:id) { blog.id }
     let(:blog) { Blog.create(title: 'foo', content: 'bar') }

test-app/spec/swagger_helper.rb

@@ -54,9 +54,9 @@ RSpec.configure do |config|
               id: { type: 'integer' },
               title: { type: 'string' },
               content: { type: 'string', nullable: true },
-              thumbnail: { type: 'string' }
+              thumbnail: { type: 'string', nullable: true }
             },
-            required: %w[id title content thumbnail]
+            required: %w[id title]
           },
           flexible_blog: {
               type: 'object',
@@ -64,9 +64,9 @@ RSpec.configure do |config|
                   id: { type: 'integer' },
                   headline: { type: 'string' },
                   text: { type: 'string', nullable: true },
-                  thumbnail: { type: 'string' }
+                  thumbnail: { type: 'string', nullable:true }
               },
-              required: %w[id headline thumbnail]
+              required: %w[id headline]
           }
         },
         securitySchemes: {

test-app/swagger/v1/swagger.json

@@ -243,7 +243,14 @@
                   "thumbnail": null
                 },
                 "schema": {
-                  "$ref": "#/components/schemas/blog"
+                  "oneOf": [
+                    {
+                      "$ref": "#/components/schemas/blog"
+                    },
+                    {
+                      "$ref": "#/components/schemas/flexible_blog"
+                    }
+                  ]
                 }
               }
             }
@@ -395,14 +402,13 @@
             "nullable": true
           },
           "thumbnail": {
-            "type": "string"
+            "type": "string",
+            "nullable": true
           }
         },
         "required": [
           "id",
-          "title",
-          "content",
-          "thumbnail"
+          "title"
         ]
       },
       "flexible_blog": {
@@ -419,13 +425,13 @@
             "nullable": true
           },
           "thumbnail": {
-            "type": "string"
+            "type": "string",
+            "nullable": true
           }
         },
         "required": [
           "id",
-          "headline",
-          "thumbnail"
+          "headline"
         ]
       }
     },