RFR: 2083: Add option for omitting messages about /approval command

[Zhao Song]

We don't need to notify users about the /approval command in all cases. So we should make it optional.

Also the term "maintainer approval" may confuse users in some cases and we also need to make it configurable.

-------------

Commit messages:
 - fix test
 - SKARA-2083

Changes: https://git.openjdk.org/skara/pull/1580/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1580&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-2083
  Stats: 43 lines in 7 files changed: 22 ins; 0 del; 21 mod
  Patch: https://git.openjdk.org/skara/pull/1580.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1580/head:pull/1580

PR: https://git.openjdk.org/skara/pull/1580