app/views/spina/admin/pages/edit_content.html.erb
<turbo-frame id="page_content">
<%= fields_for(@page) do |f| %>
<% f.fields_for "#{@locale}_content".to_sym, build_parts(f.object, @parts) do |ff| %>
<%= ff.hidden_field :type, value: ff.object.class %>
<%= ff.hidden_field :name %>
<%= ff.hidden_field :title %>
<%= render "spina/admin/parts/#{parts_partial_namespace(ff.object.class.to_s)}/form", f: ff %>
<% end %>
<% end %>
</turbo-frame>