R1:889eca1af94e

Allow a DAO object storage namespace to be forced to a particular value

Summary:
Ref T6703. When we import external data from a third-party install to a Phacility instance, we must link instance accounts to central accounts: either existing central accounts, or newly created central accounts that we send invites for.

During this import, or when users register and claim those new accounts, we do a write from `admin.phacility.com` directly into the instance database to link the accounts.

This is pretty…