Make sure webhook messages can be versionised later.

app/Services/Webhook/WebhookSenderInterface.php

@@ -0,0 +1,46 @@
+<?php
+/*
+ * WebhookSenderInterface.php
+ * Copyright (c) 2020 james@firefly-iii.org
+ *
+ * This file is part of Firefly III (https://github.com/firefly-iii).
+ *
+ * This program 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.
+ *
+ * This program 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 this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+namespace FireflyIII\Services\Webhook;
+
+use FireflyIII\Models\WebhookMessage;
+use Illuminate\Support\Collection;
+
+/**
+ * Interface WebhookSenderInterface
+ */
+interface WebhookSenderInterface
+{
+    /**
+     * @return int
+     */
+    public function getVersion(): int;
+
+    /**
+     * @param Collection $messages
+     */
+    public function setMessages(Collection $messages): void;
+
+    /**
+     *
+     */
+    public function send(): void;
+}