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Why aren’t you building 10 different apps?
Why not build 11 apps?
1 App serves as a portal for the other apps, and in the portal you can navigate (custom requesthandlers etc) between the other 10 apps without logging in in every app.
That way you only configure SSO once, but keep the performance app specific.
It is a question of monolith applications vs microservices. Monolith seems to be easier to build and if saves some repeatable tasks, but it can quickly reach the level where you cannot effectively maintain or grow. Microservices are more difficult to build, but they can grow independently of each other.
In you case, configuration of SSO and email is a one time activity; maintenance of 10 merged applications is a perpetual problem. To make an educated decision compare money saved on configuration of 10 SSOs with the cost of maintenance of the merged applications.