Case C-652/19: Judgment of the Court (Second Chamber) of 17 March 2021 (request for a preliminary ruling from the Tribunale di Milano — Italy) — KO v Consulmarketing SpA, in liquidation (Reference for a preliminary ruling — Social policy — Directive 1999/70/EC — Framework agreement on fixed-term work concluded by ETUC, UNICE and CEEP — Clause 4 — Principle of non-discrimination — Objective reasons justifying different treatment of fixed-term workers — Directive 98/59/EC — Collective redundancy — National legislation on the protection to be afforded to a worker dismissed as part of an unlawful collective redundancy — Application of a less advantageous protection system to fixed-term contracts concluded before its entry into force and converted into contracts of an indefinite duration after that date)