Handle ActionController::ParameterMissing globally

See 6d11fac2.

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Fix module inclusion in API::Utilities::UrlHelper

The stub implementation of `url_for` provided by
`ActionView::Helpers::UrlHelper` must be overridden by
`Rails.application.routes.url_helpers`:
https://github.com/rails/rails/blob/433ad334fa46623f4b218d3bb34e3f63d5481c18/actionview/lib/action_view/helpers/url_helper.rb#L31

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Update asset paths in Themes specs

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Reload translations in CustomFieldsController spec

Signed-off-by: Alex Coles <alex@alexbcoles.com>