Migrated remaining relation permission usages

Now all tests are passing.
Some level of manual checks to do.

app/Uploads/Image.php

@@ -2,10 +2,12 @@
 
 namespace BookStack\Uploads;
 
+use BookStack\Auth\Permissions\JointPermission;
 use BookStack\Entities\Models\Page;
 use BookStack\Model;
 use BookStack\Traits\HasCreatorAndUpdater;
 use Illuminate\Database\Eloquent\Factories\HasFactory;
+use Illuminate\Database\Eloquent\Relations\HasMany;
 
 /**
  * @property int    $id
@@ -25,6 +27,12 @@ class Image extends Model
     protected $fillable = ['name'];
     protected $hidden = [];
 
+    public function jointPermissions(): HasMany
+    {
+        return $this->hasMany(JointPermission::class, 'entity_id', 'uploaded_to')
+            ->where('joint_permissions.entity_type', '=', 'page');
+    }
+
     /**
      * Get a thumbnail for this image.
      *