Deprecate Pool::getGroups

This function does not work and it throws a RuntimeError because
the internal the array  property adminGroups changed some time
ago its content, but this function was not updated.

UPGRADE-3.x.md

@@ -28,6 +28,7 @@ Argument 2 of `Sonata\AdminBundle\Model\ModelManagerInterface::createQuery()` me
   Use `Sonata\AdminBundle\SonataConfiguration::getLogo()` instead.
 - `Sonata\AdminBundle\Admin\Pool::getOption()` method has been deprecated.
   Use `Sonata\AdminBundle\SonataConfiguration::getOption()` instead.
+- `Sonata\AdminBundle\Admin\Pool::getGroups()` method has been deprecated.
 
 ### Sonata\AdminBundle\Admin\FieldDescriptionInterface
 

src/Admin/Pool.php

@@ -153,8 +153,20 @@ public function __construct(
         $this->propertyAccessor = $propertyAccessor;
     }
 
+    /**
+     * NEXT_MAJOR: Remove this method.
+     *
+     * @deprecated since sonata-project/admin-bundle 3.x and will be removed in 4.0.
+     *
+     * @return array
+     */
     public function getGroups()
     {
+        @trigger_error(sprintf(
+            'Method "%s()" is deprecated since sonata-project/admin-bundle 3.x and will be removed in version 4.0.',
+            __METHOD__
+        ), E_USER_DEPRECATED);
+
         $groups = $this->adminGroups;
 
         foreach ($this->adminGroups as $name => $adminGroup) {

tests/Admin/PoolTest.php

@@ -18,11 +18,14 @@
 use Sonata\AdminBundle\Admin\AdminInterface;
 use Sonata\AdminBundle\Admin\Pool;
 use Sonata\AdminBundle\Templating\MutableTemplateRegistryInterface;
+use Symfony\Bridge\PhpUnit\ExpectDeprecationTrait;
 use Symfony\Component\DependencyInjection\Container;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 
 class PoolTest extends TestCase
 {
+    use ExpectDeprecationTrait;
+
     /**
      * @var Container
      */
@@ -40,6 +43,11 @@ protected function setUp(): void
         $this->pool = new Pool($this->container, 'Sonata Admin', '/path/to/pic.png', ['foo' => 'bar']);
     }
 
+    /**
+     * NEXT_MAJOR: Remove this method.
+     *
+     * @group legacy
+     */
     public function testGetGroups(): void
     {
         $this->container->set('sonata.user.admin.group1', $this->createMock(AdminInterface::class));
@@ -50,6 +58,8 @@ public function testGetGroups(): void
             'adminGroup1' => ['sonata.user.admin.group1' => []],
         ]);
 
+        $this->expectDeprecation('Method "Sonata\AdminBundle\Admin\Pool::getGroups()" is deprecated since sonata-project/admin-bundle 3.x and will be removed in version 4.0.');
+
         $result = $this->pool->getGroups();
         $this->assertArrayHasKey('adminGroup1', $result);
         $this->assertArrayHasKey('sonata.user.admin.group1', $result['adminGroup1']);