Question: Missing foreign key constraint from users to namespaces

Hi,

I was doing some nasty stuff this morning, deleting users in the database (DELETE FROM users, DELETE FROM identities). However, this left some user data hanging in the namespaces table and gave me a hard-to-debug error when trying to recreate the user (because there was already a conflicting namespace record.)

I know deleting data right in the database is not the best of ideas (...) but it still made me curious: there are many foreign key constraints that makes deletion of a users record also cascade to delete related data. Is there a particular reason why the associated namespace is not set up via a foreign key relation per se?

(One obvious reason I can think of: namespaces can be connected to either a team or a user, so a proper foreign key relation is hard to set up in this case.)