Case T-313/20: Judgment of the General Court of 17 May 2023 — Stadtwerke Leipzig v Commission (Competition — Concentrations — German electricity market — Decision declaring the concentration compatible with the internal market — Action for annulment — Standing to bring proceedings — Admissibility — Obligation to state reasons — Definition of ‘single concentration’ — Right to effective judicial protection — Right to be heard — Definition of the market — Analysis period — Analysis of market power — Decisive influence — Manifest errors of assessment — Duty of care)