Upgrade Rails to version 5.2.0 (#5898)

config/initializers/cors.rb

@@ -0,0 +1,26 @@
+# Be sure to restart your server when you modify this file.
+
+# Avoid CORS issues when API is called from the frontend app.
+# Handle Cross-Origin Resource Sharing (CORS) in order to accept cross-origin AJAX requests.
+
+# Read more: https://github.com/cyu/rack-cors
+
+Rails.application.config.middleware.insert_before 0, Rack::Cors do
+  allow do
+    origins '*'
+
+    resource '/@:username',
+      headers: :any,
+      methods: [:get],
+      credentials: false
+    resource '/api/*',
+      headers: :any,
+      methods: [:post, :put, :delete, :get, :patch, :options],
+      credentials: false,
+      expose: ['Link', 'X-RateLimit-Reset', 'X-RateLimit-Limit', 'X-RateLimit-Remaining', 'X-Request-Id']
+    resource '/oauth/token',
+      headers: :any,
+      methods: [:post],
+      credentials: false
+  end
+end