Rework modal component

The component now behaves like a standard dialog:

  * closes on the current page, rather than redirecting elsewhere;
  * the close button is a standard dialog closing form;
  * the `open` attribute is removed, thus allowing ESC keypress
    to close the modal, and creating a focus trap when open. The
    previous behavior (i.e. have the modal open by default) is
    achieved via the new Stimulus controller, which on connect
    opens the dialog via JS.

admin/app/components/solidus_admin/ui/modal/component.html.erb

@@ -14,13 +14,13 @@
         <h3 class="text-xl font-semibold text-gray-900">
           <%= @title %>
         </h3>
-        <%= render component('ui/button').new(
-          tag: :a,
-          href: @close_path,
-          icon: 'close-line',
-          scheme: :ghost,
-          title: t('.close'),
-        ) %>
+        <form method="dialog">
+          <%= render component('ui/button').new(
+            icon: 'close-line',
+            scheme: :ghost,
+            title: t('.close'),
+          ) %>
+        </form>
       </header>
 
       <div class="p-4 overflow-auto">

admin/app/components/solidus_admin/ui/modal/component.js

@@ -0,0 +1,7 @@
+import { Controller } from "@hotwired/stimulus";
+
+export default class extends Controller {
+  connect() {
+    this.element.showModal();
+  }
+}

admin/app/components/solidus_admin/ui/modal/component.rb

@@ -3,7 +3,7 @@
 class SolidusAdmin::UI::Modal::Component < SolidusAdmin::BaseComponent
   renders_one :actions
 
-  def initialize(title:, close_path: nil, open: true, **attributes)
+  def initialize(title:, close_path: nil, open: false, **attributes)
     @title = title
     @close_path = close_path
     @attributes = attributes