Opt into the Gin content form routes (edit theme)

Fix #229

Implements hook_gin_content_form_routes for both the alert banner creation
and edit form. This makes editing the alert banner like nodes.

Renames the publishing options group meta to auto pick up gin theming.
Moves the revision log and new revision into the meta group
Add a flag if this is the Gin theme, if it is add the extra class to meta
so it is themed like nodes.

localgov_alert_banner.module

@@ -150,3 +150,16 @@ function localgov_alert_banner_preprocess_field(&$variables) {
     }
   }
 }
+
+/**
+ * Implements hook_gin_content_form_routes().
+ */
+function localgov_alert_banner_gin_content_form_routes() {
+  return [
+    // Alert banner add form.
+    'entity.localgov_alert_banner.add_form',
+
+    // Alert banner add form edit form.
+    'entity.localgov_alert_banner.edit_form',
+  ];
+}

src/Form/AlertBannerEntityForm.php

@@ -71,6 +71,9 @@ public function buildForm(array $form, FormStateInterface $form_state) {
     $entity = $this->entity;
     assert($entity instanceof AlertBannerEntity);
 
+    // Flag if this is Gin admin theme.
+    $is_gin_theme = $this->themeManager->getActiveTheme()->getName() == 'gin' ? TRUE : FALSE;
+
     if (!$entity->isNew()) {
       $form['new_revision'] = [
         '#type' => 'checkbox',
@@ -83,8 +86,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
     // Create the vertical tabs like on node edit forms.
     // @src https://drupal.stackexchange.com/a/276907
     // Only do this if the theme is not gin! Issue #116.
-    // @todo Opt alert banner into gin admin theming.
-    if ($this->themeManager->getActiveTheme()->getName() != 'gin') {
+    if (!$is_gin_theme) {
       $form['#theme'][] = 'node_edit_form';
       $form['#attached']['library'] = ['node/drupal.node'];
 
@@ -135,18 +137,14 @@ public function buildForm(array $form, FormStateInterface $form_state) {
     // Move the authoring info into sidebar like nodes.
     $form['uid']['#group'] = 'author';
     $form['created']['#group'] = 'author';
-    $form['revision_log_message']['#group'] = 'author';
-
-    // Move new revision into author group.
-    $form['new_revision']['#group'] = 'author';
 
     // Change the Title label.
     unset($form['title']['widget'][0]['value']['#description']);
 
     // Change the Link text description.
     $form['link']['widget'][0]['title']['#description'] = $this->t("If you don't write anything here, we will use: More information");
 
-    $form['publishing_options'] = [
+    $form['meta'] = [
       '#type' => 'details',
       '#title' => $this->t('Publishing options'),
       '#group' => 'advanced',
@@ -158,9 +156,20 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       ],
     ];
 
-    // Move publishing options into sidebar like nodes.
-    $form['display_title']['#group'] = 'publishing_options';
-    $form['remove_hide_link']['#group'] = 'publishing_options';
+    // Add the extra entity-meta__header only if this is gin theme to correctly
+    // pad the sidebar.
+    if ($is_gin_theme) {
+      $form['meta']['#attributes']['class'][] = 'entity-meta__header';
+    }
+
+    // Move new revision into meta group like nodes.
+    $form['revision_log']['#group'] = 'meta';
+    $form['new_revision']['#group'] = 'meta';
+
+    // Move publishing options meta group like nodes.
+    $form['display_title']['#group'] = 'meta';
+    $form['remove_hide_link']['#group'] = 'meta';
+
     // Status.
     unset($form['status']);
     unset($form['moderation_state']);
@@ -173,12 +182,12 @@ public function buildForm(array $form, FormStateInterface $form_state) {
     else {
       $status_message = $this->t('Stored %type', ['%type' => $entity->getEntityType()->getLabel()]);
     }
-    $form['publishing_options']['status-message'] = [
+    $form['meta']['status-message'] = [
       '#type' => 'markup',
       '#markup' => $status_message,
       '#weight' => -10,
     ];
-    $form['publishing_options']['status-change'] = [
+    $form['meta']['status-change'] = [
       '#type' => 'checkbox',
       '#title' => $entity->isPublished() ? $this->t('Remove') : $this->t('Set live'),
       '#description' => $this->t('On submission proceed to confirmation form to change the live status.'),