Raise an error for remote url in StatusFinder (#4776)

* Raise an error for remote url in StatusFinder

Previous implementation had allowed remote url with status id which also exists on local.

Then that bug leads /api/web/embed to return wrong embed url.

* Fix oembed_controller_spec

spec/controllers/api/oembed_controller_spec.rb

@@ -8,6 +8,7 @@ RSpec.describe Api::OEmbedController, type: :controller do
 
   describe 'GET #show' do
     before do
+      request.host = Rails.configuration.x.local_domain
       get :show, params: { url: account_stream_entry_url(alice, status.stream_entry) }, format: :json
     end