Redirect to streaming_api_base_url (#3579)

* Redirect to streaming_api_base_url

When Rails receives a request to streaming API, it most likely
means that there is another host which is configured to respond
to it. This is to redirect clients to that host if
`STREAMING_API_BASE_URL` is set as another host.

* Use the new Ruby 1.9 hash syntax

app/controllers/api/v1/streaming_controller.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+class Api::V1::StreamingController < ApiController
+  respond_to :json
+
+  def index
+    if Rails.configuration.x.streaming_api_base_url != request.host
+      uri = URI.parse(request.url)
+      uri.host = URI.parse(Rails.configuration.x.streaming_api_base_url).host
+      redirect_to uri.to_s, status: 301
+    else
+      raise ActiveRecord::RecordNotFound
+    end
+  end
+end