Improve `updaterelayfee` JSON response

Using updaterelayfee with eclair v0.6.2 returns the following:

{
  "4881ea3050bd0d82a571db79984a4c1c432eb77a7349b1afac6198b92d740cca": "RES_SUCCESS(CMD_UPDATE_RELAY_FEE(null,10 msat,150,None),4881ea3050bd0d82a571db79984a4c1c432eb77a7349b1afac6198b92d740cca) (of class fr.acinq.eclair.channel.RES_SUCCESS)"
}

We should instead return something like:

{
  "4881ea3050bd0d82a571db79984a4c1c432eb77a7349b1afac6198b92d740cca": {
    "feeBase": 10,
    "feeProportionalMillionths": 150
  }
}

Or in case of error:

{
  "4881ea3050bd0d82a571db79984a4c1c432eb77a7349b1afac6198b92d740cca": "error message"
}

If possible, we should probably also fix #2001 at the same time.

[pm47]

Agree as well. We could have a generic success field, and a specific detailed field:

{
  "success": true,
  "details": {
    "feeBaseMsat": 1000,
    "feeProportionalMillionths": 100
  }
}

And in this case really annoying. As you need to know the channels of the node to check the call worked.

I don’t get this. You would only need to do this if you call several nodes or channels at once, and in that case there is no other way but check each individual response. Otherwise just make one call per channel?

[n1bor]

Also with these APIs a simple common “result”:“ok” or similar for all calls would make life easier for users (in addition to the detailed info). Save having to have custom analysis of each call that needs testing/updating when changes are made.

And in this case really annoying. As you need to know the channels of the node to check the call worked.