[backport 1.2.x] Migrate publishing to go via new Sonatype Central publishing portal

[chadlwilson]

Backports #294 to v1.2.x

[chadlwilson]

@kares I'd like to do a (hopefully finalish) 1.2.4 release with the currently unreleased patch to support later Rails versions.

I suspect this PR will be needed before your normal release process to Maven Central works again, since OSSRH was retired on June 30, but I am making assumptions about how the org.jruby.rack namespace is managed.

Assuming you have the relevant permissions (publish portal API key, GPG signing key), do you want to have a go at a 1.2.4 release with this PR merged?

[kares]

about how the org.jruby.rack namespace is managed

The name-space is shared with jruby (org.jruby).

Just logged into central seems my OSSRH account was migrated.
Going to give give release a try, if there are hurdles than I would just leave it to JRuby core...

[chadlwilson]

Nice, looks like it worked fine!