app/views/versions/_open_ui.html.erb
<%= form_with url: open_item_version_index_path(item_id: @cocina_object.externalIdentifier),
method: :post,
local: true do %>
<div class='mb-3'>
<label for="description">Version description</label><br>
<textarea id="description" name="description" class='form-control' required="true"></textarea>
</div>
<button type='submit' class='btn btn-primary'>
Open Version
</button>
<% end %>