I have 2 Wordpress installation: siteA and siteB. Each installation have their own wordpress database: databaseA for siteA and databaseB for siteB.
What I want is users on siteA can connect on siteB. I can't use CUSTOM_USER_TABLE beacause is 2 separate databases. However the database are hosted on the same server. So, how can I use the users table of siteA for siteB with my configuration?