Case C-511/19: Judgment of the Court (Third Chamber) of 15 April 2021 (request for a preliminary ruling from the Areios Pagos — Greece) — AB v Olympiako Athlitiko Kentro Athinon — Spyros Louis (Reference for a preliminary ruling — Social policy — Directive 2000/78/EC — Principle of equal treatment in employment and occupation — Prohibition of discrimination on grounds of age — Workers placed under a labour reserve system until termination of their contract of employment — Wage reduction and reduction or loss of severance pay — System applicable to public-sector workers close to full-time retirement — Reduction of public-sector wage costs — Article 6(1) — Legitimate social policy objective — Economic crisis)