RandomBeacon contract for the Beacon Ethereum chain - sortition functions

[pdyraga]

Depends on #3062

Refs #3006

This PR implements Ethereum chain functions for Random Beacon Sortition Pool. The following functions are implemented for Ethereum:

OperatorToStakingProvider() (chain.Address, bool, error)
EligibleStake(stakingProvider chain.Address) (*big.Int, error)
IsPoolLocked() (bool, error)
IsOperatorInPool() (bool, error)
JoinSortitionPool() error

Some additional changes were necessary to instantiate RandomBeacon and SortitionPool contract references:

• The base Ethereum chain needs to provide the chain ID, transaction mutex, nonce manager, and mining waiter.
• We need to ensure there is just one instance of transaction mutex. This mutex is held by the base Ethereum chain so there has to be only one instance of Ethereum base chain. The idea is to call global Connect only one time and create all the chain instances only one time. Creating chain instances outside of Connect is not possible from the outside of ethereum package.
• We do not need to instantiate ethclient.Client outside of Connect, this is the action that should be executed upon establishing the connection, so Connect function is the right place.

[pdyraga]

There are no unit tests for Ethereum implementation, as they would require having an Ethereum client instance running. This will be covered by system tests. To test functions during the review, the following simple implementation can be used along with scripts/install.sh and scripts/initialize.sh:

package ethereum

import (
	"context"
	"fmt"
	"testing"

	"github.com/keep-network/keep-common/pkg/chain/ethereum"
)

func TestBeaconChain_KnownOperator(t *testing.T) {
	ctx := context.Background()

	config := ethereum.Config{}

	config.URL = "http://127.0.0.1:8545"
	config.Account.KeyFile = "/Users/piotr/dev/ethereum/data/keystore/UTC--2018-11-01T06-24-04.418691008Z--65ea55c1f10491038425725dc00dffeab2a1e28a"
	config.Account.KeyFilePassword = "password"
	config.ContractAddresses = make(map[string]string)
	config.ContractAddresses["RandomBeacon"] = "0x33a4bB615E56bB7538cFF511C4dc0A66fb1B27F8"

	beacon, _, err := Connect(ctx, config)
	if err != nil {
		t.Fatal(err)
	}

	stakingProvider, ok, err := beacon.OperatorToStakingProvider()
	if err != nil {
		t.Fatal(err)
	}
	fmt.Printf("stakingProvider = %v, ok = %v\n", stakingProvider, ok)

	eligibleStake, err := beacon.EligibleStake("0x65ea55c1f10491038425725dc00dffeab2a1e28a")
	if err != nil {
		t.Fatal(err)
	}
	fmt.Printf("eligibleStake = %v\n", eligibleStake)

	eligibleStake, err = beacon.EligibleStake("0x33a4bB615E56bB7538cFF511C4dc0A66fb1B27F8")
	if err != nil {
		t.Fatal(err)
	}
	fmt.Printf("eligibleStake = %v\n", eligibleStake)

	isPoolLocked, err := beacon.IsPoolLocked()
	if err != nil {
		t.Fatal(err)
	}
	fmt.Printf("isPoolLocked = %v\n", isPoolLocked)

	isOperatorInPool, err := beacon.IsOperatorInPool()
	if err != nil {
		t.Fatal(err)
	}
	fmt.Printf("isOperatorInPool = %v\n", isOperatorInPool)

	err = beacon.JoinSortitionPool()
	if err != nil {
		t.Fatal(err)
	}

	isOperatorInPool, err = beacon.IsOperatorInPool()
	if err != nil {
		t.Fatal(err)
	}
	fmt.Printf("isOperatorInPool = %v\n", isOperatorInPool)
}