wallet: expose a coin distribution endpoint for utxo summary statistics

[turbomaze]

Usage:

curl http://x:apikey@localhost:14039/wallet/:wallet/coin-distribution\?bucketExponent\=10

Output:

{
  "distributions": [
    [
      {
        "minValue": 0,
        "maxValue": 100000,
        "counts": { "OPEN": 9, "REGISTER": 1, "RENEW": 1 },
        "totalValue": 0
      },
      {
        "minValue": 100000,
        "maxValue": 1000000,
        "counts": { "NONE": 4 },
        "totalValue": 3975060
      },
      {
        "minValue": 1000000,
        "maxValue": 10000000,
        "counts": { "REDEEM": 5, "REGISTER": 2, "NONE": 2 },
        "totalValue": 15990580
      },
      {
        "minValue": 10000000,
        "maxValue": 100000000,
        "counts": {},
        "totalValue": 0
      },
      {
        "minValue": 100000000,
        "maxValue": 1000000000,
        "counts": { "NONE": 1 },
        "totalValue": 100000000
      },
      {
        "minValue": 1000000000,
        "maxValue": 10000000000,
        "counts": { "NONE": 1831 },
        "totalValue": 3661854639960
      }
    ]
  ]
}

[RevCBH]

Presumably we will want to be able to get this information across backends, too. Right?

[turbomaze]

Yes, I structured the response as an array of distributions so that the shape to the client is consistent if we're returning 1 distribution or 10. The load balancer layer can accumulate distributions in the same distribution key

[RevCBH]

LGTM