DB: Updated handling of deleted user ID handling in DB

Updated uses of user ID to nullify on delete.
Added testing to cover deletion of user relations.
Added model factories to support changes and potential other tests.
Cleans existing ID references in the DB via migration.

app/Entities/Models/Deletion.php

@@ -4,6 +4,7 @@ namespace BookStack\Entities\Models;
 
 use BookStack\Activity\Models\Loggable;
 use BookStack\Users\Models\User;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\MorphTo;
@@ -17,6 +18,8 @@ use Illuminate\Database\Eloquent\Relations\MorphTo;
  */
 class Deletion extends Model implements Loggable
 {
+    use HasFactory;
+
     protected $hidden = [];
 
     /**

app/Entities/Models/PageRevision.php

@@ -6,6 +6,7 @@ use BookStack\Activity\Models\Loggable;
 use BookStack\App\Model;
 use BookStack\Users\Models\User;
 use Carbon\Carbon;
+use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 
 /**
@@ -30,6 +31,8 @@ use Illuminate\Database\Eloquent\Relations\BelongsTo;
  */
 class PageRevision extends Model implements Loggable
 {
+    use HasFactory;
+
     protected $fillable = ['name', 'text', 'summary'];
     protected $hidden = ['html', 'markdown', 'text'];