- Group/GroupMembership/ModuleGrant models plus MembershipSource enum
(D-05), placed under TenantModuleActivation with German block comment
- Hand-SQL appended to the generated migration: partial unique index for
one default group per tenant (D-13), CHECK num_nonnulls xor-constraint
plus two partial unique indexes for ModuleGrant (D-04), and the D-06
backfill (Group -> GroupMembership -> ModuleGrant, each INSERT guarded
by WHERE NOT EXISTS for idempotent re-runs on `prisma migrate deploy`)
- apps/api/src/groups/migration-sql.spec.ts verifies the hand-SQL by
reading migration.sql directly, no DB required
- Verified against the local DB: default-group count matches tenant
count, membership/grant counts match existing users/active
activations, and the XOR constraint rejects a group+user-less insert
