Changes plugin language based on user's locale

lib/Config/Initializer.php

@@ -232,6 +232,7 @@ class Initializer {
       $this->setupHooks();
       $this->setupJSONAPI();
       $this->setupRouter();
+      $this->setupUserLocale();
     } catch(\Exception $e) {
       $this->handleFailedInitialization($e);
     }
@@ -247,6 +248,13 @@ class Initializer {
     $router->init();
   }
 
+  function setupUserLocale() {
+    if(get_user_locale() === get_locale()) return;
+    unload_textdomain(Env::$plugin_name);
+    $localizer = new Localizer();
+    $localizer->init();
+  }
+
   function setupPages() {
     $pages = new \MailPoet\Settings\Pages();
     $pages->init();

lib/Config/Localizer.php

@@ -30,7 +30,7 @@ class Localizer {
   function locale() {
     $locale = apply_filters(
       'plugin_locale',
-      get_locale(),
+      get_user_locale(),
       Env::$plugin_name
     );
     return $locale;