List id from settings should be used if none is provided via partial render locals

[itschn]

• list_id from Settings
• placeholder from translations
• submit_button_message from translations
• disable_with_message from translations

<%= form_for MailService::Customer.new, url: mailfox.newsletter_subscribe_path, as: :newsletter, remote: true, html: { class: 'mailfox-newsletter-form' } do |f| %>
  <%= f.hidden_field :list_id, value: list_id %>
  <%= f.text_field :email, placeholder: placeholder, class: 'mailfox-newsletter-input' %>
  <%= f.submit submit_button_message, class: 'mailfox-newsletter-submit', data: { disable_with: disable_with_message } %>
  <div class="mailfox-newsletter-msg"></div>
<% end %>

link to file: https://github.com/HitFox/mailfox/blob/master/app/views/mailfox/newsletters/_form.html.erb