Opinion 1/19: Opinion of the Court (Grand Chamber) of 6 October 2021 — European Parliament (Opinion pursuant to Article 218(11) TFEU — Convention on preventing and combating violence against women and domestic violence (Istanbul Convention) — Signature by the European Union — Draft conclusion by the European Union — Concept of an ‘agreement envisaged’, within the meaning of Article 218(11) TFEU — External competences of the European Union — Substantive legal basis — Article 78(2) TFEU — Article 82(2) TFEU — Article 83(1) TFEU — Article 84 TFEU — Article 336 TFEU — Articles 1 to 4a of Protocol (No 21) on the position of the United Kingdom and Ireland in respect of the area of freedom, security and justice — Partial participation of Ireland in the conclusion of the Istanbul Convention by the European Union — Possibility of splitting the act concluding an international agreement into two separate decisions according to the applicable legal bases — Practice of ‘common accord’ — Compatibility with the TEU and the TFEU)