List balances

Ledger balances of the merchant's settlement account in the caller's mode. `available_units` can be paid out; `pending_units` is awaiting confirmation; `locked_units` is reserved by in-flight operations. `usd_value` is null when no rate is available.

curl -X GET 'http://127.0.0.1:3001/v1/balances'

{  "object": "list",  "data": [    {      "object": "balance",      "asset": "string",      "chain": "string",      "decimals": 0,      "available_units": "string",      "pending_units": "string",      "locked_units": "string",      "usd_value": "string"    }  ]}