Issues Subscription different Types

[6543]

Migrate to new Types

current: true (1), false(0)

aim: IssueWatchModeNone, IssueWatchModeNormal, IssueWatchModeDont, IssueWatchModeAuto

ToDo

• DB migration
• Update Related code
• new Function to get Types
• extend subscription API
  GET /repos/{owner}/{repo}/issues/{index}/subscriptions/{user}
• ignore issue if unsubscribed but repowatch

Notes

IssueWatchModeNone = not watching / no DB entry
IssueWatchModeNormal = subscribed to issue (manualy)
IssueWatchModeDont = explisit unsubscribe
IssueWatchModeAuto = subscribed by automation (write a comment at this issue)

RepoWatch should respect IssueWatchModeDont in future ...

[6543]

this should close part of #145 (Automatic subscribe on Open/Comment, etc)

[6543]

WIP PR: #9535