relay_fee result should be strongly typed

[rustaceanrob]

From the docs:

Returns the minimum accepted fee by the server’s node in Bitcoin, not Satoshi.

That last nuance is irrelevant if the API just returns the Amount type. Same thing should be done for estimate_fee to use FeeRate, but that one is non-trivial.

[ValuedMammal]

I know the docs aren't clear in this regard but I think it would make sense for this to return a FeeRate which I believe was the approach in #136 also.

[rustaceanrob]

I don't know the electrum protocol, my interpretation of the docs was this is an absolute fee that a transaction must have, so an Amount is the fee required to broadcast with that node.

If this is actually a fee rate in bitcoin per vbyte then the docs should be updated accordingly before any attempt at a PR to return FeeRate

[oleonardolima]

I also interpret the docs as this one being an absolute fee, but some validation on electrum code besides documentation is needed.

[ValuedMammal]

To be clear I'm referring to "relay fee" as described in getnetworkinfo RPC if indeed that's what this method refers to. https://bitcoincore.org/en/doc/28.0.0/rpc/network/getnetworkinfo/

I agree that the value can be parsed as an amount in BTC (same for estimate_fee), but that still leaves #136 unresolved where the user has to interpret the value as a useful feerate.

this is an absolute fee that a transaction must have, so an Amount is the fee required to broadcast with that node

If you consider test_relay_fee below, that would be saying that the blockstream server refuses to relay anything that pays less than 1000 sats in fees which I don't think is the case.