Innkeeper: monitor tenant settings and database usage

It would be nice for the innkeeper to be able to have a glimpse at some key elements of each tenant's wallet to assess whether undesirable usage patterns are in use, and what steps to take on next.

Some items that would be nice to see:
- tenant-specific settings: this is already visible by accessing the tenant with a temporary api-key
- exchange record/connection record persistence and state
- database usage: table size and, potentially, breakdown by element type (connection, exchange, etc.)

No files, tests, or entry points are named. Start by reviewing how an innkeeper accesses a tenant with a temporary API key and how exchange and connection records are persisted; done means defining a way to inspect tenant settings, record states, table size, and any element-type breakdown.

Written by the indexing model from the issue text.