add specs to ensure mime type is still set correctly

Author: JRfromAustria

spec/errors_spec.rb

@@ -31,6 +31,7 @@
 
       it do
         expect(response).to have_http_status(:unprocessable_entity)
+        expect(response.media_type).to eq("application/vnd.api+json")
         expect(response_json['errors'].size).to eq(1)
         expect(response_json['errors'][0]['status']).to eq('422')
         expect(response_json['errors'][0]['title'])

spec/fetching_spec.rb

@@ -25,6 +25,7 @@
         it do
           expect(response).to have_http_status(:ok)
           expect(response_json['data'].size).to eq(users.size)
+          expect(response.media_type).to eq("application/vnd.api+json")
 
           response_json['data'].each do |item|
             user = users.detect { |u| u.id == item['id'].to_i }