Added reference storage system, and command to re-index

Also re-named/orgranized some files for this, to make them "References"
specific instead of a subset of "Util".

app/Console/Commands/RegenerateCommentContent.php

@@ -5,6 +5,7 @@ namespace BookStack\Console\Commands;
 use BookStack\Actions\Comment;
 use BookStack\Actions\CommentRepo;
 use Illuminate\Console\Command;
+use Illuminate\Support\Facades\DB;
 
 class RegenerateCommentContent extends Command
 {
@@ -43,9 +44,9 @@ class RegenerateCommentContent extends Command
      */
     public function handle()
     {
-        $connection = \DB::getDefaultConnection();
+        $connection = DB::getDefaultConnection();
         if ($this->option('database') !== null) {
-            \DB::setDefaultConnection($this->option('database'));
+            DB::setDefaultConnection($this->option('database'));
         }
 
         Comment::query()->chunk(100, function ($comments) {
@@ -55,7 +56,8 @@ class RegenerateCommentContent extends Command
             }
         });
 
-        \DB::setDefaultConnection($connection);
+        DB::setDefaultConnection($connection);
         $this->comment('Comment HTML content has been regenerated');
+        return 0;
     }
 }

app/Console/Commands/RegeneratePermissions.php

@@ -50,5 +50,6 @@ class RegeneratePermissions extends Command
 
         DB::setDefaultConnection($connection);
         $this->comment('Permissions regenerated');
+        return 0;
     }
 }

app/Console/Commands/RegenerateReferences.php

@@ -0,0 +1,58 @@
+<?php
+
+namespace BookStack\Console\Commands;
+
+use BookStack\References\ReferenceService;
+use Illuminate\Console\Command;
+use Illuminate\Support\Facades\DB;
+
+class RegenerateReferences extends Command
+{
+    /**
+     * The name and signature of the console command.
+     *
+     * @var string
+     */
+    protected $signature = 'bookstack:regenerate-references {--database= : The database connection to use.}';
+
+    /**
+     * The console command description.
+     *
+     * @var string
+     */
+    protected $description = 'Regenerate all the cross-item model reference index';
+
+    protected ReferenceService $references;
+
+    /**
+     * Create a new command instance.
+     *
+     * @return void
+     */
+    public function __construct(ReferenceService $references)
+    {
+        $this->references = $references;
+        parent::__construct();
+    }
+
+    /**
+     * Execute the console command.
+     *
+     * @return int
+     */
+    public function handle()
+    {
+        $connection = DB::getDefaultConnection();
+
+        if ($this->option('database')) {
+            DB::setDefaultConnection($this->option('database'));
+        }
+
+        $this->references->updateForAllPages();
+
+        DB::setDefaultConnection($connection);
+
+        $this->comment('References have been regenerated');
+        return 0;
+    }
+}