Add Announce validator and test

app/Util/ActivityPub/Validator/Announce.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace App\Util\ActivityPub\Validator;
+
+use Validator;
+use Illuminate\Validation\Rule;
+
+class Announce {
+
+	public static function validate($payload)
+	{
+		$valid = Validator::make($payload, [
+			'@context' => 'required',
+			'id' => 'required|string',
+			'type' => [
+				'required',
+				Rule::in(['Announce'])
+			],
+			'actor' => 'required|url|active_url',
+			'published' => 'required|date',
+			'to'	=> 'required',
+			'cc'	=> 'required',
+			'object' => 'required|url|active_url'
+		])->passes();
+
+		return $valid;
+	}
+}