Case C-310/19 P: Judgment of the Court (Ninth Chamber) of 4 June 2020 — Boudewijn Schokker v European Union Aviation Safety Agency (Appeal — Civil service — Contract staff — Recruitment procedure — Classification in grade — Conditions of Employment of Other Servants — Article 86 — European Union Aviation Safety Agency (EASA) — General implementing provisions — Challenge of the proposed classification — Withdrawal of the offer of employment — Action for compensation — Principle of sound administration — Duty to have regard for the welfare of staff — Breach of administrative duty — Non-contractual liability of the European Union — Non-material damage — Compensation)