Voting Connector: Support vote rewards

[PJColombo]

This PR builds on top of #336 and addreses the DeepDao's Gitcoin bounty related to supporting vote rewards.

It adds a new functionality to the Vote model that allows you to get all the actions inside the vote script which is a set of codified DAO's app contract calls that are executed once the vote is enacted.

An action has the following fields:

• to: The target contract address.
• fnData: Data related to the function being called.
  -- abi: the ABI function fragment.
  -- roles: The ACL roles needed to execute the function.
  -- sig: The function signature (e.g. transfer(address,address,uint256)).
  -- params: The function parameter values.
  -- notice: The function radspec description.
• rewards: An array containing all the action rewards. A reward has the following fields:
  -- amount: The reward's token amount.
  -- receiver: The account that receives the reward.
  -- token: The reward's token contract address.

If an action involves a token transfer from the DAO to an account then the rewards field is filled.

Right now, the following are considered to be token transfer actions:

• Calls to the Vault/Agent's contract function transfer(address _token, address _to, uint256 _value).
• Calls to the Finance's contract function newImmediatePayment(address _token, address _receiver, uint256 _amount, string _reference).

If you want to quickly test the connector with these changes you can use a private subgraph that I deployed just for testing: https://thegraph.com/hosted-service/subgraph/pjcolombo/connect-voting-status

You only need to change the VOTING_SUBGRAPH_URL variable value here.

[kanaagawa]

Great work and well done with the unit testing. Reading them made me realize that the final structure you choose for the data was the right one. I left a couple of comments and an open question about your thoughts for the getRewards function.

[pmlambert]

@0xGabi I spent a nice chunk of time not knowing this 🥇

[Rekard0]

the tests did not ran successfully, even after swapping the VOTING_SUBGRAPH_URL as stated in the PR description.

• can you provide more context or instruction how you run test locally?
• Is there a way to run the test successfully without swapping the URL?