[PLUGIN][ActivityPub] Finish base ActivityStreams 2.0 interface

Instructions below

To extend an Activity properties do:

public function onActivityPubValidateActivityStreamsTwoData(string $type_name, array &$validators): bool {
    if ($type_name === '{Type}') {
        $validators['attribute'] = myValidator::class;
    }
    return Event::next;
}

The Validator should be of the form:

use ActivityPhp\Type;
use ActivityPhp\Type\Util;
use Plugin\ActivityPub\Util\ModelValidator;

class myValidator extends ModelValidator
{
    /**
     * Validate Attribute's value
     *
     * @param mixed $value from JSON's attribute
     * @param mixed $container A {Type}
     * @return bool
     * @throws Exception
     */
    public function validate($value, $container): bool
    {
        // Validate that container is a {Type}
        Util::subclassOf($container, Type\Extended\Object\{Type}::class, true);

        return {Validation Result};

To act on received activities do:

public function onActivityPubNew{Type}(&$obj): bool {

To add information to Activities being federated by ActivityPub do:

public function ActivityPubAddActivityStreamsTwoData(string $type_name, &$type): bool {

To implement an ActivityStreams 2.0 representation do:

public function onActivityPubActivityStreamsTwoResponse(string $route, arrray $vars, ?TypeResponse &$response = null): bool {
        if ($route === '{Object route}') {
                $response = ModelResponse::handle($vars[{Object}]);
                return Event::stop;
        }
        return Event::next;
}

plugins/ActivityPub/Util/ModelValidator.php

@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+// {{{ License
+// This file is part of GNU social - https://www.gnu.org/software/social
+//
+// GNU social is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// GNU social is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with GNU social.  If not, see <http://www.gnu.org/licenses/>.
+// }}}
+
+/**
+ * ActivityPub implementation for GNU social
+ *
+ * @package   GNUsocial
+ * @category  ActivityPub
+ * @author    Diogo Peralta Cordeiro <@diogo.site>
+ * @copyright 2021 Free Software Foundation, Inc http://www.fsf.org
+ * @license   https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
+ */
+
+namespace Plugin\ActivityPub\Util;
+
+use ActivityPhp\Type\ValidatorInterface;
+use ActivityPhp\Type\ValidatorTools;
+
+/**
+ * \Plugin\ActivityPub\Util\ModelValidator is an abstract class for
+ * attribute validation.
+ * Its purpose is to be extended by Plugin\ActivityPub\Util\Validator\*
+ * classes.
+ * It provides some methods to make some regular validations.
+ * It implements \ActivityPhp\Type\ValidatorInterface.
+ *
+ * @copyright 2021 Free Software Foundation, Inc http://www.fsf.org
+ * @license   https://www.gnu.org/licenses/agpl.html GNU AGPL v3 or later
+ */
+abstract class ModelValidator extends ValidatorTools implements ValidatorInterface
+{
+}