Case C-681/21, BVAEB (Amount of the retirement pension): Judgment of the Court (Seventh Chamber) of 27 April 2023 (request for a preliminary ruling from the Verwaltungsgerichtshof — Austria) — Versicherungsanstalt öffentlich Bediensteter, Eisenbahnen und Bergbau (BVAEB) v BB (Reference for a preliminary ruling — Social policy — Equal treatment in employment and occupation — Directive 2000/78/EC — Prohibition of discrimination on grounds of age — Retirement pension — National legislation providing, with retroactive effect, for a category of civil servants previously advantaged by the national legislation relating to retirement pension rights to be treated in the same way as a category of civil servants previously disadvantaged by that legislation)