Add Orderable capacity and per-user permission filtering for GLPI 11 custom assets

Following review feedback on #574, replace the unconditional
auto-registration of all active custom asset definitions with an explicit,
admin-controlled opt-in via a new Orderable capacity:

- Introduce PluginOrderOrderableCapacity (extends \Glpi\Asset\Capacity\AbstractCapacity).
  Admins enable/disable it per asset definition under
  Setup -> Asset definitions -> {asset} -> Capacities. Provides label, icon,
  description, and a usage count based on existing PluginOrderReference rows.

- In plugin_init_order(), register the capacity with AssetDefinitionManager,
  then iterate active definitions and append the generated asset class to
  $ORDER_TYPES only when:
    1. the Orderable capacity is enabled on that definition, AND
    2. the current user passes $class::canView()
       (which delegates to the asset's AssignableItem READ check + is_active).

- The class_exists() guard preserves backward compatibility on GLPI <= 10.x.

End-to-end tested on GLPI 11.0.6, PHP 8.3, Order plugin 2.12.6:
- Capacity appears in the Capacities tab with proper label/icon/description.
- With capacity disabled: custom asset is absent from the Item type dropdown.
- With capacity enabled: custom asset appears, references can be created,
  Generate item massive action renders and submits, items reach Taken
  delivery state, and generated assets appear in the Assets section.
- Native itemtypes remain unaffected.

Addresses review comments from @stonebuzz on #574.

Author: bygadd

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [unreleased]
 
+### Added
+- Add an `Orderable` capacity for GLPI 11 custom asset definitions, allowing each definition to opt-in to being used as a Product reference itemtype. Asset classes are filtered by per-user read permission.
+
 ### Fixed
 
 - Fix generate associated item massive action

inc/orderablecapacity.class.php

@@ -0,0 +1,45 @@
+<?php
+
+/**
+ * Capacity that flags a GLPI 11 custom asset definition as orderable
+ * through the Order plugin. When enabled on an asset definition (Setup ->
+ * Asset definitions -> {your asset} -> Capacities), the corresponding
+ * generated asset class is appended to $ORDER_TYPES and becomes selectable
+ * as an Item type when creating a Product reference.
+ */
+class PluginOrderOrderableCapacity extends \Glpi\Asset\Capacity\AbstractCapacity
+{
+    public function getLabel(): string
+    {
+        return __('Orderable', 'order');
+    }
+
+    public function getIcon(): string
+    {
+        return 'ti ti-shopping-cart';
+    }
+
+    public function getDescription(): string
+    {
+        return __(
+            'Allow this asset to be referenced as a Product reference and '
+            . 'generated from the Generate item massive action.',
+            'order'
+        );
+    }
+
+    public function getCapacityUsageDescription(string $classname): string
+    {
+        $count = 0;
+        if (class_exists('PluginOrderReference')) {
+            $count = countElementsInTable(
+                \PluginOrderReference::getTable(),
+                ['itemtype' => $classname]
+            );
+        }
+        return sprintf(
+            _n('Used by %d order reference', 'Used by %d order references', $count, 'order'),
+            $count
+        );
+    }
+}

setup.php

@@ -125,6 +125,29 @@ function plugin_init_order()
             'Pdu',
         ];
 
+
+        // Register the Orderable capacity for GLPI 11 custom assets and append
+        // any custom asset class that has it enabled to $ORDER_TYPES, provided
+        // the current user is allowed to view it.
+        if (class_exists(\Glpi\Asset\AssetDefinitionManager::class)) {
+            $asset_manager = \Glpi\Asset\AssetDefinitionManager::getInstance();
+            $orderable_capacity = new PluginOrderOrderableCapacity();
+            $asset_manager->registerCapacity($orderable_capacity);
+            $asset_manager->bootDefinitions();
+            foreach ($asset_manager->getDefinitions(true) as $definition) {
+                if (!$definition->hasCapacityEnabled($orderable_capacity)) {
+                    continue;
+                }
+                $custom_asset_class = $definition->getAssetClassName();
+                if (
+                    !in_array($custom_asset_class, $ORDER_TYPES, true)
+                    && $custom_asset_class::canView()
+                ) {
+                    $ORDER_TYPES[] = $custom_asset_class;
+                }
+            }
+        }
+
         $CFG_GLPI['plugin_order_types'] = $ORDER_TYPES;
 
         $PLUGIN_HOOKS['pre_item_purge']['order'] = [