We're building a SaaS with a friend, and we pretty much finished the product's core's "mvp", but now we have to build... everything else

Users managements, "groups" of users, billing, access control,...

Pretty much everything that makes a SaaS... a SaaS. And I feel like I'm continuously discovering new things that seem essential, which is both awesome and disheartening.

So, what books, blogs, videos, online courses, whatever, would you consider are a must-read ( / watch / listen...) for someone who has never built a SaaS, or even a real product's backend for that matter ^^'

Also, anything related to event-driven architectures would be awesome :-) (I read Martin Fowler's posts and watched his video. They're quite fascinating)

(I'm originally a mobile dev who's been playing around with serverless for the last 2 1/2 years ^^')