Case C-566/17: Judgment of the Court (Second Chamber) of 8 May 2019 (request for a preliminary ruling from the Wojewódzki Sąd Administracyjny we Wrocławiu — Poland) — Związek Gmin Zagłębia Miedziowego w Polkowicach v Szef Krajowej Administracji Skarbowej (Reference for a preliminary ruling — Common system of value added tax (VAT) — Directive 2006/112/EC — Article 168(a) — Deduction of input tax — Principle of VAT neutrality — Taxable person engaged in both economic and non-economic activities — Goods and services purchased for the purposes of performing both transactions subject to VAT and non-taxable transactions — Absence of apportionment criteria in national legislation — Principle of lawfulness of the tax)