Who is asking, whose submission it is, and where it goes.

The system of record for tenants, for submission intake and for routing. A request for cover arrives here and is routed from here; every other product carries the identifiers and keeps no registry of its own.

Owns tenancy. Every other product treats a tenant as an opaque id and enforces its own isolation.
Owns intake and routing — one place a submission is created, and one place it is retired.
No foreign key crosses into it. A sibling’s migration is never another product’s problem.