Geth ethereum node communication

[mederic-p]

Issue/Task Number: #693
Closes #693

Overview

This PR refactors the blockchain and eth_blockchain sub-apps and adds the support for the geth adapter.

Changes

• Rename blockchain to eth_blockchain
• Rename blockchain_eth to geth_eth_adapter
• Move wallet generation to eth_blockchain sub-app
• Add ethereumex and abi dependencies to handle JSON-RPC calls to geth
• Add genserver handler for {:get_balances, address, contract_addresses, block} that returns a map of contract_address -> balance for the specified wallet address
• Add default_adapter config that is set to :geth by default except for tests where it's set to :dumb which is a Dumb adapter that mock responses.

Usage

• Set the url of a JSON-RPC server in eth_geth_adapter/config/dev.exs
• Have a valid wallet address with an eth balance and optionally a few ERC20 tokens balances.
• Run the elixir console: iex -S mix
• Call

EthBlockchain.Balance.get({"0x54e0588607dcec6c0b36fca1154a57814a913591",  ["0x48b91d5f363892592bf836777dc73b54a10b72ae", "0x0000000000000000000000000000000000000000", "0x436dbc182828ccd421238fb622613c953c5e5028", "0xb76fe945f8672b57cc151448e2f52b0f88891c34"]})

(replace the first param with your wallet address and the list of addresses with the actual contract addresses).

Note: the 0x0000000000000000000000000000000000000000 represents the Eth token.

• Receive a response:

{:ok,
 %{
   "0x0000000000000000000000000000000000000000" => 13155000000000000000000,
   "0x436dbc182828ccd421238fb622613c953c5e5028" => 10000000000,
   "0x48b91d5f363892592bf836777dc73b54a10b72ae" => 999999999999999999999999900,
   "0xb76fe945f8672b57cc151448e2f52b0f88891c34" => 0 
 }}

For future PRs:

• Refactor response handler/parser if new JSON call need to use them
• Improve the setting/config setup for the blockchain adapters

[sirn]

I’ll do another pass later today.

[sirn]

Should we remove this and use only dumb adapter?

[sirn]

Might worth switching this to EthBlockchainCase. Probably make it return supervisor pid as well? (Since we need to perform the which_children check?)

[sirn]

Maybe we should ask Mana-Ethereum people to support {:system, ...} style config 😉

[sirn]

I think the worker shouldn’t access Keychain directly. Instead, let the EthBlockchain pass it to the adapter (so the adapter can be self-contained).

[unnawut]

LGTM but let's wait for a few more 👍