The behaviors of closing issues and reopening issues are very different.
So splitting it into two different functions makes it easier to
maintain.
- [x] Split ChangeIssueStatus into CloseIssue and ReopenIssue both at
the service layer and model layer
- [x] Rename `isClosed` to `CloseOrReopen` to make it more readable.
- [x] Add transactions for ReopenIssue and CloseIssue
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Co-authored-by: Zettat123 <zettat123@gmail.com>