Upgrade to Rails 5.2

All the code in the `bin/` and the `config/` folder has been generated
running `rake app:update`, except the `escape_javascript_fix` file,
which we've removed since the code there is already included in Rails
5.2.

config/environments/development.rb

@@ -13,12 +13,13 @@ Rails.application.configure do
   config.consider_all_requests_local = true
 
   # Enable/disable caching. By default caching is disabled.
-  if Rails.root.join("tmp/caching-dev.txt").exist?
+  # Run rails dev:cache to toggle caching.
+  if Rails.root.join("tmp", "caching-dev.txt").exist?
     config.action_controller.perform_caching = true
 
     config.cache_store = :memory_store
     config.public_file_server.headers = {
-      "Cache-Control" => "public, max-age=172800"
+      "Cache-Control" => "public, max-age=#{2.days.to_i}"
     }
   else
     config.action_controller.perform_caching = false
@@ -41,6 +42,9 @@ Rails.application.configure do
   # Raise an error on page load if there are pending migrations.
   config.active_record.migration_error = :page_load
 
+  # Highlight code that triggered database queries in logs.
+  config.active_record.verbose_query_logs = true
+
   # Debug mode disables concatenation and preprocessing of assets.
   # This option may cause significant delays in view rendering with a large
   # number of complex assets.

config/environments/test.rb

@@ -20,7 +20,7 @@ Rails.application.configure do
   # Configure public file server for tests with Cache-Control for performance.
   config.public_file_server.enabled = true
   config.public_file_server.headers = {
-    "Cache-Control" => "public, max-age=3600"
+    "Cache-Control" => "public, max-age=#{1.hour.to_i}"
   }
 
   # Show full error reports and disable caching.