Added expireat(key, timestamp)` method (#97)

Author: sevrugin

src/M6Web/Component/RedisMock/RedisMock.php

@@ -164,12 +164,17 @@ public function ttl($key)
     }
 
     public function expire($key, $seconds)
+    {
+        return $this->expireat($key, time() + $seconds);
+    }
+
+    public function expireat($key, $timestamp)
     {
         if (!array_key_exists($key, self::$dataValues[$this->storage]) || $this->deleteOnTtlExpired($key)) {
             return $this->returnPipedInfo(0);
         }
 
-        self::$dataTtl[$this->storage][$key] = time() + $seconds;
+        self::$dataTtl[$this->storage][$key] = $timestamp;
 
         return $this->returnPipedInfo(1);
     }