Adds version support to public API

lib/API/Endpoints/v1/CustomFields.php

@@ -0,0 +1,57 @@
+<?php
+namespace MailPoet\API\Endpoints\v1;
+use MailPoet\API\Endpoint as APIEndpoint;
+use MailPoet\API\Error as APIError;
+use MailPoet\Models\CustomField;
+
+if(!defined('ABSPATH')) exit;
+
+class CustomFields extends APIEndpoint {
+  function getAll() {
+    $collection = CustomField::orderByAsc('created_at')->findMany();
+    $custom_fields = array_map(function($custom_field) {
+      return $custom_field->asArray();
+    }, $collection);
+
+    return $this->successResponse($custom_fields);
+  }
+
+  function delete($data = array()) {
+    $id = (isset($data['id']) ? (int)$data['id'] : null);
+    $custom_field = CustomField::findOne($id);
+    if($custom_field === false) {
+      return $this->errorResponse(array(
+        APIError::NOT_FOUND => __('This custom field does not exist.', 'mailpoet')
+      ));
+    } else {
+      $custom_field->delete();
+
+      return $this->successResponse($custom_field->asArray());
+    }
+  }
+
+  function save($data = array()) {
+    $custom_field = CustomField::createOrUpdate($data);
+    $errors = $custom_field->getErrors();
+
+    if(!empty($errors)) {
+      return $this->badRequest($errors);
+    } else {
+      return $this->successResponse(
+        CustomField::findOne($custom_field->id)->asArray()
+      );
+    }
+  }
+
+  function get($data = array()) {
+    $id = (isset($data['id']) ? (int)$data['id'] : null);
+    $custom_field = CustomField::findOne($id);
+    if($custom_field === false) {
+      return $this->errorResponse(array(
+        APIError::NOT_FOUND => __('This custom field does not exist.', 'mailpoet')
+      ));
+    } else {
+      return $this->successResponse($custom_field->asArray());
+    }
+  }
+}