add controller specs

spec/factories/codeharbor_link.rb

@@ -0,0 +1,8 @@
+FactoryBot.define do
+  factory :codeharbor_link do
+    user { build(:teacher) }
+    push_url { 'http://push.url' }
+    check_uuid_url { 'http://check-uuid.url' }
+    sequence(:api_key) { |n| "api_key#{n}" }
+  end
+end