Scenario: I have a website which was initially developed with a single site (A) in mind. Now, because reasons, I need to make this a multi-site setup (A & B). So, I have functionality in A I want to share with B. We built A with all config exported to it's config sync folder, which means all config is intertwined.
Problem: How would I go about converting all sharable configuration to modules, which would allow me to maintain the modules from one codebase in both A & B? Putting everything into
module_foobar/config/install/ will not work that easily for A, since it already has that config in it's active config.