FEATURE: add site setting allow_new_registrations which can be used to block all new account registrations

spec/controllers/users_controller_spec.rb

@@ -269,6 +269,7 @@ describe UsersController do
 
   describe '#create' do
     before do
+      SiteSetting.stubs(:allow_new_registrations).returns(true)
       @user = Fabricate.build(:user)
       @user.password = "strongpassword"
       DiscourseHub.stubs(:register_username).returns([true, nil])
@@ -291,6 +292,14 @@ describe UsersController do
         expect(response.status).to eq(500)
       end
 
+      it 'returns an error when new registrations are disabled' do
+        SiteSetting.stubs(:allow_new_registrations).returns(false)
+        post_user
+        json = JSON.parse(response.body)
+        json['success'].should be_false
+        json['message'].should be_present
+      end
+
       it 'creates a user correctly' do
         Jobs.expects(:enqueue).with(:user_email, has_entries(type: :signup))
         User.any_instance.expects(:enqueue_welcome_message).with('welcome_user').never
@@ -355,6 +364,14 @@ describe UsersController do
         expect(JSON.parse(response.body)['active']).to be_true
       end
 
+      it 'returns 500 status when new registrations are disabled' do
+        SiteSetting.stubs(:allow_new_registrations).returns(false)
+        post_user
+        json = JSON.parse(response.body)
+        json['success'].should be_false
+        json['message'].should be_present
+      end
+
       context 'authentication records for' do
 
         before do