feat: switch to using JSON-RPC 2.0 by default

[zivkovicmilos]

Description

This PR introduces the usage of the JSON-RPC 2.0 standard for faucet responses, which should also be adopted by all middlewares.

To request a faucet drip after this PR, the caller needs to call the method "drip".
The params for the drip are:

1. the beneficiary (required)
2. the amount (optional, defaults to max send amount of the faucet)

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "drip",
  "params": [
    "g1e6gxg5tvc55mwsn7t7dymmlasratv7mkv0rap2",
    "1000ugnot"
  ]
}

The responses will also follow the JSON-RPC 2.0 standard:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "Successful faucet transfer"
}

Error responses will look like (result is null):

{
  "error": {
    "message": "invalid beneficiary address, invalid separator index -1",
    "code": -32602
  },
  "id": 1,
  "jsonrpc": "2.0"
}

[aeddi]

Nice 👍