Automatically return added funds if bounty's Github issue is closed

[tpatja]

Description

Type: Feature

When bountied Github issue is manually closed (without merging a PR), we should return the funds transferred to the bounty contract to the senders and consider the bounty closed.

[arash009]

from @3esmit

New version (IssueBank) will work like this:

1. bounty is opened by anyone and enters open state
2. funds are sent to bounty address, they are only accepted at open state
3. prs are merged and detected by SOB, which are called by smart contract
4. when close the issue, repository owner needs to select which accounts will be rewarded from list defined by SOB in 3.
5. if issue is closed with confirmed rewards at 4., then it goes to reward state
   1. if issue is closed with no confirmed rewards at 4., then it goes to refund state
6. reward state allows accounts confirmed at 4. to take their share
   1. refund state allow accounts that deposited at 2. to take what they deposited
7. when all funds are retrieved from smart contract it enters in a finalized state
8. at finalized state, tokens sent incorrectly (that are untrackable inchain from whom sent) remaining on smart contract can be retrieved by repository owner.
9. tokens can still be sent incorrectly to bounty, or ether aswell by using selfdestruct opcode pointing to bounty address, this funds can still be retrieved at 8.

[oskarth]

this funds can still be retrieved at 8.

What's 8?

[arash009]

Copy/Paste messed up. Check again

[arash009]

It might be better if we solve this requirement without Issuebank contract changes in the first instance. Will setup a separate issue to track Issuebank implementation