MinimalMember plus what GetInitialData bolts onto it.

The extra keys only exist for a logged-in caller, hence optional.

{'user': ..., 'submodel': ...} - who is calling.

user stays open: get_serialized_user() picks a different serializer per user type (engineer, planning, customer, ...).

What product a tenant is: the web client themes and gates on this.

Instance is a Member. modules is the plain list of module names in the tenant's contract's module paths, empty when there is no contract. module_parts maps each of those modules to its enabled parts.