RFR: 1997: Allow the creator of a PR to set the commit author [v3]

[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 10 additional commits since the last revision:

 - fix tests
 - update
 - Update bots/pr/src/main/java/org/openjdk/skara/bots/pr/AuthorCommand.java
   
   Co-authored-by: Erik Joelsson <37597443+erikj79 at users.noreply.github.com>
 - Update bots/pr/src/main/java/org/openjdk/skara/bots/pr/AuthorCommand.java
   
   Co-authored-by: Erik Joelsson <37597443+erikj79 at users.noreply.github.com>
 - Update bots/pr/src/main/java/org/openjdk/skara/bots/pr/AuthorCommand.java
   
   Co-authored-by: Erik Joelsson <37597443+erikj79 at users.noreply.github.com>
 - update
 - Update bots/pr/src/main/java/org/openjdk/skara/bots/pr/CheckablePullRequest.java
   
   Co-authored-by: Erik Joelsson <37597443+erikj79 at users.noreply.github.com>
 - Update bots/pr/src/main/java/org/openjdk/skara/bots/pr/AuthorCommand.java
   
   Co-authored-by: Erik Joelsson <37597443+erikj79 at users.noreply.github.com>
 - Update bots/pr/src/main/java/org/openjdk/skara/bots/pr/AuthorCommand.java
   
   Co-authored-by: Erik Joelsson <37597443+erikj79 at users.noreply.github.com>
 - Update bots/pr/src/main/java/org/openjdk/skara/bots/pr/AuthorCommand.java
   
   Co-authored-by: Erik Joelsson <37597443+erikj79 at users.noreply.github.com>

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

Changes:
  - all: https://git.openjdk.org/skara/pull/1553/files
  - new: https://git.openjdk.org/skara/pull/1553/files/f1f3639f..f2409e82

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=skara&pr=1553&range=02
 - incr: https://webrevs.openjdk.org/?repo=skara&pr=1553&range=01-02

  Stats: 44 lines in 8 files changed: 4 ins; 3 del; 37 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