Case T-673/17: Judgment of the General Court of 20 September 2019 — Port autonome du Centre et de l’Ouest and Others v Commission (State aid — Corporate tax exemption scheme implemented by Belgium in favour of its ports — Decision declaring the aid scheme incompatible with the internal market — Concept of economic activity — Services of general economic interest — Non-economic activities — Severability — Selectivity — Article 93 TFEU and Article 106(2) TFEU)