Case C-16/18: Judgment of the Court (Grand Chamber) of 19 December 2019 (request for a preliminary ruling from the Verwaltungsgerichtshof — Austria) — Michael Dobersberger v Magistrat der Stadt Wien (Reference for a preliminary ruling — Articles 56 and 57 TFEU — Freedom to provide services — Directive 96/71/EC — Applicability — Article 1(3)(a) — Posting of workers in the framework of the provision of services — Provision of services on board international trains — National rules imposing administrative obligations in relation to the posting of workers)