Nonlocality in photonic materials and metamaterials: roadmap - Monticone, Francesco; Luo, Yu; Zheng, Xuezhi; Tserkezis, Christos; Peres, Nuno M R; Wegner, Gino; Busch, Kurt; Hu, Huatian; Zhang, Pu; Ciraci, Cristian; Aizpurua, Javier; Babaze, Antton; et al. (OPTICAL MATERIALS EXPRESS, 2025)