Add estimate fee endpoint

[paweljakubas]

Issue Number

#469

Overview

• I have added implementation of estimateFee endpoint
• I have added respective typesSpec unit tests
• I have added corresponding integration tests unifying them with already present ones

Comments

[KtorZ]

Awesome work @paweljakubas !
I haven't look in depth to the integration scenarios. From a quick glance, this looks okay, but I'll spend a bit more time later reviewing carefully and I invite @piotr-iohk to also do the same 😄

[piotr-iohk]

I've reviewed the tests - looking good, thanks a lot @paweljakubas ! :)
There's one test that could be added: estimate transaction for amount = 0. That one should behave different for http-bridge and jormungandr so they should go to their specific libs, like:

http-bridge -> https://github.com/input-output-hk/cardano-wallet/blob/master/lib/http-bridge/test/integration/Test/Integration/HttpBridge/Scenario/API/Transactions.hs

jormungandr -> https://github.com/input-output-hk/cardano-wallet/tree/master/lib/jormungandr/test/integration/Test/Integration/Jormungandr/Scenario/

[piotr-iohk]

perhaps let's also check the amount here: expectFieldBetween amount...