app/views/follow_ups/_new.html.erb
<%= simple_form_for [@case_file, @followup], as: :entry, url: case_follow_ups_path(@case_file), remote: true do |f| %>
<%= f.input :case_id, as: :hidden %>
<%= f.input :user_id, as: :hidden %>
<%= f.input :description, as: :text, input_html: { rows: 10 } %>
<hr />
<%= f.submit 'Add Follow Up', class: 'btn btn-primary btn-block' %>
<% end %>