Find route between nodes. #1068

[tompro]

Added additional method to Eclair like findRoute but allowing for 2 nodeIds. Also added a new endpoint to the http Api "findroutebetweennodes" which takes sourceNode and targetNode as params.

This is the impl of feature request #1068. The ticket is rather old so I don't know whether this is still a thing, but straightforward so I gave it a try. Depending on pull request for #1690 I will either impl the API change there or with this pull.

[codecov-io]

Codecov Report

Merging #1695 (52a4bd9) into master (2a359c6) will decrease coverage by 0.04%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master    #1695      +/-   ##
==========================================
- Coverage   86.04%   86.00%   -0.05%     
==========================================
  Files         151      151              
  Lines       11491    11500       +9     
  Branches      497      496       -1     
==========================================
+ Hits         9888     9890       +2     
- Misses       1603     1610       +7     

Impacted Files	Coverage Δ
...r-core/src/main/scala/fr/acinq/eclair/Eclair.scala	54.74% <0.00%> (-0.41%)	⬇️
...cinq/eclair/blockchain/bitcoind/zmq/ZMQActor.scala	90.00% <0.00%> (-5.00%)	⬇️
...main/scala/fr/acinq/eclair/io/PeerConnection.scala	82.97% <0.00%> (-0.86%)	⬇️
...q/eclair/blockchain/electrum/ElectrumWatcher.scala	76.98% <0.00%> (-0.80%)	⬇️
...nq/eclair/blockchain/electrum/ElectrumClient.scala	73.52% <0.00%> (-0.37%)	⬇️
...n/scala/fr/acinq/eclair/router/Announcements.scala	100.00% <0.00%> (ø)
...c/main/scala/fr/acinq/eclair/channel/Helpers.scala	96.25% <0.00%> (+0.01%)	⬆️
...re/src/main/scala/fr/acinq/eclair/NodeParams.scala	92.09% <0.00%> (+0.04%)	⬆️

[t-bast]

This PR is small enough and trivial enough to include now before our upcoming release, thanks for the contribution! Just a small nit and we should be good to go.