Voting connector: Support vote statuses

[PJColombo]

This PR updates both the Voting connector and subgraph in order to expose the vote status following the DeepDao's Gitcoin bounty requirements.

The vote status can be one of the following:

-Ongoing: The vote hasn't ended.
-Accepted: The vote ended and it's waiting to be executed (pending).
-Rejected: The vote ended and it didn't reach the minimum accepted quorum nor minimum support.
-Executed: The vote was enacted.

I didn't include Created nor Started as I considered those to be redundant and could be encapsulated in Ongoing.

The same I did with Ended since we can consider a vote either Accepted or Rejected when it has ended.

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.

[CLAassistant]

All committers have signed the CLA.

[0xGabi]

Well done! I left a minor suggestion.

I wonder if you consider using an enum for the status value instead of returning the string. What do you think of touching base with DeepDAO to know their preference about how to consume the status data?

[0xGabi]

LGTM