Case C-699/17: Judgment of the Court (Ninth Chamber) of 4 April 2019 (request for a preliminary ruling from the Verwaltungsgerichtshof — Austria) — proceedings brought by Allianz Vorsorgekasse AG (Reference for a preliminary ruling — Public Procurement — Conclusion of accession agreements with an occupational provident fund responsible for managing contributions of occupational solidarity — Conclusion requiring the agreement of employees or their representatives — Directive 2014/24/EU — Articles 49 and 56 TFEU — Principles of equal treatment and of non-discrimination — Obligation of transparency)