Created new entity Tag and migration to create new tables

module/Core/src/Entity/ShortUrl.php

@@ -42,6 +42,16 @@ class ShortUrl extends AbstractEntity implements \JsonSerializable
      * @ORM\OneToMany(targetEntity=Visit::class, mappedBy="shortUrl", fetch="EXTRA_LAZY")
      */
     protected $visits;
+    /**
+     * @var Collection|Tag[]
+     * @ORM\ManyToMany(targetEntity=Tag::class, cascade={"persist"})
+     * @ORM\JoinTable(name="short_urls_in_tags", joinColumns={
+     *     @ORM\JoinColumn(name="short_url_id", referencedColumnName="id")
+     * }, inverseJoinColumns={
+     *     @ORM\JoinColumn(name="tag_id", referencedColumnName="id")
+     * })
+     */
+    protected $tags;
 
     /**
      * ShortUrl constructor.
@@ -125,6 +135,34 @@ class ShortUrl extends AbstractEntity implements \JsonSerializable
         return $this;
     }
 
+    /**
+     * @return Collection|Tag[]
+     */
+    public function getTags()
+    {
+        return $this->tags;
+    }
+
+    /**
+     * @param Collection|Tag[] $tags
+     * @return $this
+     */
+    public function setTags($tags)
+    {
+        $this->tags = $tags;
+        return $this;
+    }
+
+    /**
+     * @param Tag $tag
+     * @return $this
+     */
+    public function addTag(Tag $tag)
+    {
+        $this->tags->add($tag);
+        return $this;
+    }
+
     /**
      * Specify data which should be serialized to JSON
      * @link http://php.net/manual/en/jsonserializable.jsonserialize.php

module/Core/src/Entity/Tag.php

@@ -0,0 +1,40 @@
+<?php
+namespace Shlinkio\Shlink\Core\Entity;
+
+use Doctrine\ORM\Mapping as ORM;
+use Shlinkio\Shlink\Common\Entity\AbstractEntity;
+
+/**
+ * Class Tag
+ * @author
+ * @link
+ *
+ * @ORM\Entity()
+ * @ORM\Table(name="tags")
+ */
+class Tag extends AbstractEntity
+{
+    /**
+     * @var string
+     * @ORM\Column(unique=true)
+     */
+    protected $name;
+
+    /**
+     * @return string
+     */
+    public function getName()
+    {
+        return $this->name;
+    }
+
+    /**
+     * @param string $name
+     * @return $this
+     */
+    public function setName($name)
+    {
+        $this->name = $name;
+        return $this;
+    }
+}