refactor default settings and implement allowed settings

Author: cklmercer

README.md

@@ -77,6 +77,37 @@ $user->settings()->forget('some.setting');
 ```
 
 ##### 6.) Set the default settings for a new model.
+
+If you define `$defaultSettings` as an array property on your model, we will use its value as the default settings for 
+any new models that are created *without* settings.
+
+_User.php_
+```
+use Cklmercer\ModelSettings\HasSettings;
+use Illuminate\Foundation\Auth\User as Authenticatable;
+
+class User extends Authenticatable 
+{
+    use HasSettings;
+
+    /**
+     * The model's default settings.
+     * 
+     * @var array
+     */
+    protected $defaultSettings = [
+    	'homepage' => '/profile'
+    ];
+
+    // truncated for brevity..
+}
+```
+
+##### 7.) Specify the settings that are allowed.
+
+If you define `$allowedSettings` as an array property then only settings which match a value within 
+the `$allowedSettings` array will be saved on the model.
+
 _User.php_
 ```
 use Cklmercer\ModelSettings\HasSettings;
@@ -87,18 +118,11 @@ class User extends Authenticatable
     use HasSettings;
 
     /**
-     * Set the model's default settings.
-     *
-     * @return void
+     * The model's allowed settings.
+     * 
+     * @var array
      */
-    protected function setDefaultSettings() 
-    {
-    	$this->settings = [
-    		'some' => [
-    			'setting' => true
-    		]
-    	];
-    }
+    protected $allowedSettings = ['homepage'];
 
     // truncated for brevity..
 }

src/HasSettings.php

@@ -12,10 +12,28 @@ trait HasSettings
     public static function bootHasSettings()
     {
         self::creating(function ($model) {
-            if (method_exists($model, 'setDefaultSettings')) {
-                $model->setDefaultSettings();
+            if ( ! $model->settings) {
+                $model->settings = $model->getDefaultSettings();
             }
         });
+
+        self::saving(function ($model) {
+            if (property_exists($model, 'allowedSettings') && is_array($model->allowedSettings)) {
+                $model->settings = array_only($model->settings, $model->allowedSettings);
+            }
+        });
+    }
+
+    /**
+     * Get the model's default settings.
+     *
+     * @return array
+     */
+    public function getDefaultSettings()
+    {
+        return (isset($this->defaultSettings) && is_array($this->defaultSettings)) 
+            ? $this->defaultSettings 
+            : [];
     }
 
     /**