Add rudimentary logger

[MAILPOET-570]

lib/Logging/Logger.php

@@ -0,0 +1,38 @@
+<?php
+
+namespace MailPoet\Logging;
+
+use MailPoet\Dependencies\Monolog\Processor\IntrospectionProcessor;
+use MailPoet\Dependencies\Monolog\Processor\MemoryUsageProcessor;
+use MailPoet\Dependencies\Monolog\Processor\WebProcessor;
+
+class Logger {
+
+  /** @var \MailPoet\Dependencies\Monolog\Logger[] */
+  private static $instance = [];
+
+  /**
+   * @param string $name
+   * @param bool $forceCreate
+   *
+   * @return \MailPoet\Dependencies\Monolog\Logger
+   */
+  public static function getLogger($name = 'MailPoet', $forceCreate = false) {
+    if(!isset(self::$instance[$name]) || $forceCreate) {
+      self::$instance[$name] = new \MailPoet\Dependencies\Monolog\Logger($name);
+
+      if(WP_DEBUG) {
+        // Adds the line/file/class/method from which the log call originated
+        self::$instance[$name]->pushProcessor(new IntrospectionProcessor());
+        // Adds the current request URI, request method and client IP to a log record
+        self::$instance[$name]->pushProcessor(new WebProcessor());
+        // Adds the current memory usage to a log record
+        self::$instance[$name]->pushProcessor(new MemoryUsageProcessor());
+      }
+
+      self::$instance[$name]->pushHandler(new LogHandler());
+    }
+    return self::$instance[$name];
+  }
+
+}