docs for metadata mapper prop

src/exposers/mappers/class-tainacan-mapper.php

@@ -7,7 +7,28 @@ abstract class Mapper {
 	public $name = null; // Public name do mapper
 	public $allow_extra_fields = true; // Allow more field to be register
 	public $context_url = null; // URL of mapper documentation
-	public $metadata = false; // array of supported metadata, false for not validade the list 
+	
+	/**
+	 * array of supported metadata, false for not validade the list format:
+	 * ['slug'] => [
+	 *     'URI' => 'http://...',          // URI of the field description
+	 *     'label' => 'Label',             // Label to show on UI
+	 *     'field_type' => 'date',         // Tainacan recomended field type, default text
+	 *     'core_field' => 'description'   // if have a core tainacan field, what?
+	 * ['date' => [
+	 *     	'URI' => 'http://purl.org/dc/elements/1.1/date',
+	 *  	'label' => 'Date',
+     *      'field_type' => 'date'
+	 *  ],
+	 *  'description' => [
+	 *  	'URI' => 'http://purl.org/dc/elements/1.1/description',
+	 *  	'label' => 'Description',
+	 *      'core_field' => 'description'
+	 *  ]]
+	 * @var array
+	 */
+	public $metadata = false;
+	
 	public $prefix = ''; // Tag prefix like "dc:"
 	public $sufix = ''; // Tag sufix
 	public $header = false; // API response header or file header to be used with