Add an accounting / historical database

[NiloCK]

go-nitro client currently has a durable store for protocol specific data: channels, objectives, signatures, etc.

There is currently no storage or aggregation of "business concerns", such as

• receipts of payments rendered, received (w/ metadata such as delivered service, counterparty, networking fees, timestamps)
• overall network balance (over time)
• openings & closings of channels
• ... maybe others?

Options:

1. Add this data to the existing DB.
2. Create a new internal API for storing non-protocol data.