Case C-645/19: Judgment of the Court (Grand Chamber) of 15 June 2021 (request for a preliminary ruling from the Hof van beroep te Brussel — Belgium) — Facebook Ireland Ltd, Facebook Inc., Facebook Belgium BVBA v Gegevensbeschermingsautoriteit (Reference for a preliminary ruling — Protection of natural persons with regard to the processing of personal data — Charter of Fundamental Rights of the European Union — Articles 7, 8 and 47 — Regulation (EU) 2016/679 — Cross-border processing of personal data — ‘One-stop shop’ mechanism — Sincere and effective cooperation between supervisory authorities — Competences and powers — Power to initiate or engage in legal proceedings)