$request: $wgRequest
$mediaWiki: The $mediawiki object
+'MediaWikiServices': Called when a global MediaWikiServices instance is
+initialized. Extensions may use this to define, replace, or wrap services.
+However, the preferred way to define a new service is
+the $wgServiceWiringFiles array.
+$services: MediaWikiServices
+
'MessageCache::get': When fetching a message. Can be used to override the key
for customisations. Given and returned message key must be in special format:
1) first letter must be in lower case according to the content language.