move requests to backend (#18)

source/includes/EventsCache.php

@@ -0,0 +1,19 @@
+<?php
+namespace MobilizonConnector;
+
+final class EventsCache {
+
+  private static $MAX_AGE_IN_S = 120;
+
+  public static function set(array $parameters, mixed $data): void {
+    // md5 is used as key must be 172 characters or fewer in length.
+    $key = md5(json_encode($parameters));
+    set_transient($key, $data, self::$MAX_AGE_IN_S);
+  }
+
+  public static function get(array $parameters): mixed {
+    $key = md5(json_encode($parameters));
+    $data = get_transient($key);
+    return $data;
+  }
+}