added PHPDocs
added PHPDoc for SolrLyricsApiHandler::getSong() and throwing 404 when results are null
fixed SolrLyricsApiHandler so it passes getSong integration test
changed mid to medium, added PHPDoc, refactored part responsible for images and reused it in two places
fixed SolrLyricsApiHandler so it passes getArtist() integration test
added more details thrown exception of LyricsApiController::getData()
added new private method to return NotFoundApiException details
added PHPDocs