Added some simple time travel mechanism for part view.

In the moment it is not possible to show elements that were deleted.

src/Entity/Contracts/TimeStampableInterface.php

@@ -0,0 +1,44 @@
+<?php
+/**
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ * Copyright (C) 2019 - 2020 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\Contracts;
+
+
+use DateTime;
+
+interface TimeStampableInterface
+{
+    /**
+     * Returns the last time when the element was modified.
+     * Returns null if the element was not yet saved to DB yet.
+     *
+     * @return DateTime|null the time of the last edit
+     */
+    public function getLastModified(): ?DateTime;
+
+    /**
+     * Returns the date/time when the element was created.
+     * Returns null if the element was not yet saved to DB yet.
+     *
+     * @return DateTime|null the creation time of the part
+     */
+    public function getAddedDate(): ?DateTime;
+}

src/Entity/Contracts/TimeTravelInterface.php

@@ -0,0 +1,41 @@
+<?php
+/**
+ * This file is part of Part-DB (https://github.com/Part-DB/Part-DB-symfony).
+ *
+ * Copyright (C) 2019 - 2020 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\Contracts;
+
+
+interface TimeTravelInterface
+{
+    /**
+     * Checks if this entry has informations which data has changed.
+     * @return bool True if this entry has informations about the changed data.
+     */
+    public function hasOldDataInformations(): bool;
+
+    /** Returns the data the entity had before this log entry. */
+    public function getOldData(): array;
+
+    /**
+     * Returns the the timestamp associated with this change.
+     * @return \DateTime
+     */
+    public function getTimestamp(): \DateTime;
+}