[Koha] Sharing patrons across libraries in Koha

Hi, In our institution we have a few libraries in different locations. All the patrons are affiliated with the institution, not with a specific library. What are your suggestions on how to organize them in Koha? It seems that Koha requires them to always be affiliated with a specific library - doesn't allow to associate them with multiple libraries at the same time and it also doesn't allow to associate them with a defined group of libraries ... Ideas please? Thanks. R