Platform
Tenancy
The (application, tenant) model that every product shares.
Everything is keyed by (app, tenant)
DevSewa is one registered application on every engine. Each of your tenants is a tenant under it: users live in a collection per (app, tenant), mail attributes every message to devsewa/<tenant>, the vault namespaces owners by it. You never see the engine’s identity for DevSewa and never call an engine directly.
One canonical spelling
Tenant names are lowercase letters, digits and single underscores. Acme-EU is refused with the spelling to use (acme_eu) rather than folded silently — folding is not injective, and three spellings would become three customers.