Add a new column for namepsace default compliance framework

Problem description

This issue is an iteration in developing Group-level setting for default compliance fram... (&8815 - closed).

Proposal

Add a new database column to store the default compliance framework of a namespace.

Implementation plan

database 2️⃣

1. Add a migration to add default_compliance_framework_id (INT) as a new column to the namespace_settings table.
2. The new column should be a foreign key to the compliance_management_frameworks(id) table.