RFR: 1997: Allow the creator of a PR to set the commit author [v4]

[Zhao Song]

> In this pr, we will introduce a new pull request command `/author`.
> 
> If an author wants to contribute a change to a repository, but he doesn't have access, then someone with the access will be able to help him with this command.
> 
> Usage: `/author [set|remove] [@user | openjdk-user | Full Name <email at address>]`
> Examples: 
> `/author set @openjdk-bot`
> `/author @openjdk-bot`
> `/author set J. Duke <duke at openjdk.org>`
> `/author remove @openjdk-bot`
> `/author remove`
> 
> Note: only Committers of the repository would be allowed to issue /author command.

Zhao Song has updated the pull request incrementally with one additional commit since the last revision:

  update

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

Changes:
  - all: https://git.openjdk.org/skara/pull/1553/files
  - new: https://git.openjdk.org/skara/pull/1553/files/f2409e82..fb88a0e2

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=skara&pr=1553&range=03
 - incr: https://webrevs.openjdk.org/?repo=skara&pr=1553&range=02-03

  Stats: 31 lines in 4 files changed: 5 ins; 0 del; 26 mod
  Patch: https://git.openjdk.org/skara/pull/1553.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1553/head:pull/1553

PR: https://git.openjdk.org/skara/pull/1553