Allow casts with a return type of static or this to reference themselves (#1103)

* Allow casts with a return type of static or this to reference themselves

Supports

```php
/**
     * @param $model
     * @param string $key
     * @param $value
     * @param array $attributes
     * @return static
     */
    public function get($model, string $key, $value, array $attributes)
    {
        return new static($value);
    }
```

or

```php
/**
     * @param $model
     * @param string $key
     * @param $value
     * @param array $attributes
     * @return $this
     */
    public function get($model, string $key, $value, array $attributes)
    {
        return new static($value);
    }
```

* Update CHANGELOG.md

tests/Console/ModelsCommand/LaravelCustomCasts/Casts/ExtendedSelfCastingCasterWithStaticDocblockReturn.php

@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Barryvdh\LaravelIdeHelper\Tests\Console\ModelsCommand\LaravelCustomCasts\Casts;
+
+use Illuminate\Contracts\Database\Eloquent\CastsAttributes;
+
+class ExtendedSelfCastingCasterWithStaticDocblockReturn extends SelfCastingCasterWithStaticDocblockReturn
+{
+
+}

tests/Console/ModelsCommand/LaravelCustomCasts/Casts/ExtendedSelfCastingCasterWithThisDocblockReturn.php

@@ -0,0 +1,12 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Barryvdh\LaravelIdeHelper\Tests\Console\ModelsCommand\LaravelCustomCasts\Casts;
+
+use Illuminate\Contracts\Database\Eloquent\CastsAttributes;
+
+class ExtendedSelfCastingCasterWithThisDocblockReturn extends SelfCastingCasterWithStaticDocblockReturn
+{
+    
+}

tests/Console/ModelsCommand/LaravelCustomCasts/Casts/SelfCastingCasterWithStaticDocblockReturn.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Barryvdh\LaravelIdeHelper\Tests\Console\ModelsCommand\LaravelCustomCasts\Casts;
+
+use Illuminate\Contracts\Database\Eloquent\CastsAttributes;
+
+class SelfCastingCasterWithStaticDocblockReturn implements CastsAttributes
+{
+    /**
+     * @return static
+     */
+    public function get($model, string $key, $value, array $attributes)
+    {
+        return new static();
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function set($model, string $key, $value, array $attributes)
+    {
+        // TODO: Implement set() method.
+    }
+}

tests/Console/ModelsCommand/LaravelCustomCasts/Casts/SelfCastingCasterWithThisDocblockReturn.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Barryvdh\LaravelIdeHelper\Tests\Console\ModelsCommand\LaravelCustomCasts\Casts;
+
+use Illuminate\Contracts\Database\Eloquent\CastsAttributes;
+
+class SelfCastingCasterWithThisDocblockReturn implements CastsAttributes
+{
+    /**
+     * @return $this
+     */
+    public function get($model, string $key, $value, array $attributes)
+    {
+        return new static();
+    }
+
+    /**
+     * @inheritDoc
+     */
+    public function set($model, string $key, $value, array $attributes)
+    {
+        // TODO: Implement set() method.
+    }
+}