RFR: 1715: Configure custom default security level for new backport issues in notifier

[Erik Joelsson]

This patch makes it possible to configure a default security level to use for any newly created backport in the IssueNotifier. The configuration is done per repository and branch, with a regex for matching branch names. This is what it would look like in the bot configuration.


"issue": {
  "project": "bugs/JDK",
  "fixversions": {},
  "buildname": "master",
  "headversion": true,
  "defaultsecurity": {  // <- new
    "jdk.*": "10000",
  }
}


If the parent bug already has a security level, then that is inherited, just like today, otherwise this new default value is used.

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Commit messages:
 - SKARA-1715

Changes: https://git.openjdk.org/skara/pull/1445/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1445&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1715
  Stats: 136 lines in 6 files changed: 125 ins; 0 del; 11 mod
  Patch: https://git.openjdk.org/skara/pull/1445.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1445/head:pull/1445

PR: https://git.openjdk.org/skara/pull/1445