Feature request: credit deal auto-repayment

[abitmore]

User Story

As a borrower, I would like that my debt can be (optionally) repaid automatically when it comes due and I have a sufficient balance in my account, so that I don't accidentally lose my collateral. If I don't have a sufficient balance in my account at that time, (optionally) repay as much as possible.

I also want my debt to have an optional auto-renewal when it comes to due. (This has been moved to a new issue: https://github.com/bitshares/bitshares-core/issues/2734 .)

Impacts Describe which portion(s) of BitShares Core may be impacted by your request. Please tick at least one box.

• [ ] API (the application programming interface)
• [ ] Build (the build process or something prior to compiled code)
• [ ] CLI (the command line wallet)
• [ ] Deployment (the deployment process after building such as Docker, Travis, etc.)
• [ ] DEX (the Decentralized EXchange, market engine, etc.)
• [ ] P2P (the peer-to-peer network for transaction/block propagation)
• [ ] Performance (system or user efficiency, etc.)
• [x] Protocol (the blockchain logic, consensus, validation, etc.)
• [ ] Security (the security of system or user data, etc.)
• [x] UX (the User Experience)
• [ ] Other (please add below)

CORE TEAM TASK LIST

• [ ] Evaluate / Prioritize Feature Request
• [ ] Refine User Stories / Requirements
• [ ] Define Test Cases
• [ ] Design / Develop Solution
• [ ] Perform QA/Testing
• [ ] Update Documentation

[abitmore]

Done via #2735.