DEV: Introduce <DPageHeader /> and <DPageSubheader /> components (#30146)

This converts the `<AdminPageHeader />` component and the
`<AdminPageSubheader />` components into new components
that can be used outside of admin, and updates the CSS classes.
Also introduces a `<DPageActionButton />` component and child
components for the header action buttons.

I have to keep the old admin-only components around for
now until plugins are updated, then we can remove it,
and remove the re-exports that are done within
admin-page-action-button.gjs

spec/system/admin_flags_spec.rb

@@ -8,7 +8,7 @@ describe "Admin Flags Page", type: :system do
   let(:admin_flags_page) { PageObjects::Pages::AdminFlags.new }
   let(:admin_flag_form_page) { PageObjects::Pages::AdminFlagForm.new }
   let(:flag_modal) { PageObjects::Modals::Flag.new }
-  let(:admin_header) { PageObjects::Components::AdminHeader.new }
+  let(:d_page_header) { PageObjects::Components::DPageHeader.new }
 
   before do
     sign_in(admin)
@@ -27,7 +27,7 @@ describe "Admin Flags Page", type: :system do
     )
 
     admin_flags_page.visit
-    expect(admin_header).to be_visible
+    expect(d_page_header).to be_visible
 
     admin_flags_page.toggle("spam")
     topic_page.visit_topic(post.topic).open_flag_topic_modal
@@ -81,8 +81,7 @@ describe "Admin Flags Page", type: :system do
     expect(admin_flags_page).to have_add_flag_button_enabled
 
     admin_flags_page.click_add_flag
-
-    expect(admin_header).to be_hidden
+    expect(d_page_header).to be_hidden
 
     admin_flag_form_page
       .fill_in_name("Vulgar")
@@ -115,7 +114,7 @@ describe "Admin Flags Page", type: :system do
 
     # update
     admin_flags_page.visit.click_edit_flag("custom_vulgar")
-    expect(admin_header).to be_hidden
+    expect(d_page_header).to be_hidden
     admin_flag_form_page.fill_in_name("Tasteless").click_save
 
     expect(admin_flags_page).to have_flags(
@@ -158,7 +157,7 @@ describe "Admin Flags Page", type: :system do
   it "has settings tab" do
     admin_flags_page.visit
 
-    expect(admin_header).to have_tabs(
+    expect(d_page_header).to have_tabs(
       [I18n.t("admin_js.settings"), I18n.t("admin_js.admin.config_areas.flags.flags_tab")],
     )
 

spec/system/admin_user_fields_spec.rb

@@ -6,11 +6,11 @@ describe "Admin User Fields", type: :system do
   before { sign_in(current_user) }
 
   let(:user_fields_page) { PageObjects::Pages::AdminUserFields.new }
-  let(:admin_header) { PageObjects::Components::AdminHeader.new }
+  let(:page_header) { PageObjects::Components::DPageHeader.new }
 
   it "correctly saves user fields" do
     user_fields_page.visit
-    expect(admin_header).to be_visible
+    expect(page_header).to be_visible
     user_fields_page.add_field(name: "Occupation", description: "What you do for work")
 
     expect(user_fields_page).to have_user_field("Occupation")
@@ -32,7 +32,7 @@ describe "Admin User Fields", type: :system do
     user_fields_page.visit
     user_fields_page.click_add_field
 
-    expect(admin_header).to be_hidden
+    expect(page_header).to be_hidden
 
     form = page.find(".user-field")
     editable_label = I18n.t("admin_js.admin.user_fields.editable.title")
@@ -73,7 +73,7 @@ describe "Admin User Fields", type: :system do
 
       form.find(".user-field-name").fill_in(with: "Favourite Transformer")
 
-      expect(admin_header).to be_hidden
+      expect(page_header).to be_hidden
 
       form.find(".btn-primary").click
 

spec/system/page_objects/components/admin_header.rb

@@ -2,17 +2,18 @@
 
 module PageObjects
   module Components
+    # TODO (martin) Delete this after plugins have been updated to use DPageHeader
     class AdminHeader < PageObjects::Pages::Base
       def has_tabs?(names)
-        expect(page.all(".admin-nav-submenu__tabs a").map(&:text)).to eq(names)
+        expect(page.all(".d-nav-submenu__tabs a").map(&:text)).to eq(names)
       end
 
       def visible?
-        has_css?(".admin-page-header")
+        has_css?(".d-page-header")
       end
 
       def hidden?
-        has_no_css?(".admin-page-header")
+        has_no_css?(".d-page-header")
       end
     end
   end

spec/system/page_objects/components/d_page_header.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+module PageObjects
+  module Components
+    class DPageHeader < PageObjects::Pages::Base
+      def has_tabs?(names)
+        expect(page.all(".d-nav-submenu__tabs a").map(&:text)).to eq(names)
+      end
+
+      def visible?
+        has_css?(".d-page-header")
+      end
+
+      def hidden?
+        has_no_css?(".d-page-header")
+      end
+    end
+  end
+end

spec/system/page_objects/pages/admin_plugins_list.rb

@@ -21,7 +21,7 @@ module PageObjects
       end
 
       def plugin_nav_tab_selector(plugin)
-        ".admin-nav-submenu__tabs .admin-plugin-tab-nav-item[data-plugin-nav-tab-id=\"#{plugin}\"]"
+        ".d-nav-submenu__tabs .admin-plugin-tab-nav-item[data-plugin-nav-tab-id=\"#{plugin}\"]"
       end
     end
   end

spec/system/page_objects/pages/admin_user_fields.rb

@@ -19,7 +19,7 @@ module PageObjects
       end
 
       def click_add_field
-        page.find(".admin-page-header__actions .btn-primary").click
+        page.find(".d-page-header__actions .btn-primary").click
       end
 
       def click_edit