Innkeeper: monitor tenant settings and database usage

[esune]

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.)