Changed DB structure the way, many more elements can have attachments

Also every Element has now a preview attachment field. For the user this will be used as profile picture.

src/Entity/Base/MasterAttachmentTrait.php

@@ -0,0 +1,78 @@
+<?php
+/**
+ *
+ * part-db version 0.1
+ * Copyright (C) 2005 Christoph Lechner
+ * http://www.cl-projects.de/
+ *
+ * part-db version 0.2+
+ * Copyright (C) 2009 K. Jacobs and others (see authors.php)
+ * http://code.google.com/p/part-db/
+ *
+ * Part-DB Version 0.4+
+ * Copyright (C) 2016 - 2019 Jan Böhmer
+ * https://github.com/jbtronics
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA
+ *
+ */
+
+namespace App\Entity\Base;
+
+
+use App\Entity\Attachments\Attachment;
+use App\Entity\Parts\Part;
+use App\Security\Annotations\ColumnSecurity;
+use Symfony\Component\Validator\Constraints as Assert;
+
+/**
+ * A entity with this class has a master attachment, which is used as a preview image for this object.
+ * @package App\Entity\Parts\PartTraits
+ */
+trait MasterAttachmentTrait
+{
+    /**
+     * @var Attachment
+     * @ORM\ManyToOne(targetEntity="App\Entity\Attachments\Attachment")
+     * @ORM\JoinColumn(name="id_preview_attachement", referencedColumnName="id")
+     * @Assert\Expression("value == null or value.isPicture()", message="part.master_attachment.must_be_picture")
+     * @ColumnSecurity(prefix="attachments", type="object")
+     */
+    protected $master_picture_attachment;
+
+
+    /**
+     * Get the master picture "Attachment"-object of this part (if there is one).
+     * The master picture should be used as a visual description/representation of this part.
+     * @return Attachment the master picture Attachement of this part (if there is one)
+     */
+    public function getMasterPictureAttachment(): ?Attachment
+    {
+        return $this->master_picture_attachment;
+    }
+
+    /**
+     * Sets the new master picture for this part.
+     * @param Attachment|null $new_master_attachment
+     * @return Part
+     */
+    public function setMasterPictureAttachment(?Attachment $new_master_attachment): self
+    {
+        $this->master_picture_attachment = $new_master_attachment;
+        return $this;
+    }
+
+
+}