Added test for logical-theme-system command registration

Changed how the command registration was handled due to complications of
action order found during testing. Now the theme service will resolve
and directly register the command on the Kernel instead of them being
fetched from the ThemeService from within Kernel.
More direct, Seems to work.

tests/ThemeTest.php

@@ -7,8 +7,10 @@ use BookStack\Entities\Models\Page;
 use BookStack\Entities\Tools\PageContent;
 use BookStack\Facades\Theme;
 use BookStack\Theming\ThemeEvents;
+use Illuminate\Console\Command;
 use Illuminate\Http\Request;
 use Illuminate\Http\Response;
+use Illuminate\Support\Facades\Artisan;
 use Illuminate\Support\Facades\File;
 use League\CommonMark\ConfigurableEnvironmentInterface;
 
@@ -206,6 +208,16 @@ class ThemeTest extends TestCase
         $this->assertStringContainsString('donkey=donut', $redirect);
     }
 
+    public function test_register_command_allows_provided_command_to_be_usable_via_artisan()
+    {
+        Theme::registerCommand(new MyCustomCommand);
+
+        Artisan::call('bookstack:test-custom-command', []);
+        $output = Artisan::output();
+
+        $this->assertStringContainsString('Command ran!', $output);
+    }
+
     protected function usingThemeFolder(callable $callback)
     {
         // Create a folder and configure a theme
@@ -220,3 +232,10 @@ class ThemeTest extends TestCase
         File::deleteDirectory($themeFolderPath);
     }
 }
+
+class MyCustomCommand extends Command {
+    protected $signature = 'bookstack:test-custom-command';
+    public function handle() {
+        $this->line('Command ran!');
+    }
+}