I have a WordPress multisite (network) running on a master theme which I cloned. Outside of the multisite I have another WordPress site which I use to aggregate (aggregator) content from the network.
I'm exploring cost-efficient options to build out an SSO, which would use the aggregator site as the authentication locale, and if a user registers to any of the sites in the network, they would be both registered to all the sites in the network and to the aggregator.
I've explored a few mainstream options i:e Miniorange, Okta.. but all work on an instance-based pricing model.. which makes building a network of hundreds of sites quite expensive. Yeah.. I'm bootstrapping.
Any recommendations for open source or service providers where this type of infrastructure could be possible, secure, scalable and affordable?