#new-photo-message
  = semantic_form_for PhotoMessage.new, url: thread_photos_path(@thread), html: {multipart: true} do |f|
    = f.inputs do
      = f.input :photo, as: :file
      = f.input :retained_photo, as: :hidden
      = f.input :caption
      = semantic_fields_for Message.new do |f2|
        = f2.input :body
    = f.buttons do
      = f.commit_button

#new-photo-message
  = semantic_form_for PhotoMessage.new, url: thread_photos_path(@thread), html: {multipart: true} do |f|
    = f.inputs do
      = f.input :photo, as: :file
      = f.input :retained_photo, as: :hidden
      = f.input :caption
    = f.buttons do
      = f.commit_button

Remove message field from photo message, prefer caption.
Remove message field from photo message, prefer caption.
