expose a global constant that identifies running inside KB

this could prove useful for plugins (despite the configuration .yml being used less), desired sample :

:stripe:
  :api_secret_key: <%= ENV['API_SECRET_KEY'] %>
  :api_publishable_key: <%= ENV['API_PUBLISHABLE_KEY'] %>
  :test: true

<% if defined? KILLBILL_VERSION %>
:database:
  :adapter: mariadb
  :jndi: 'killbill/osgi/jdbc'
  :pool: 100
<% else %>
:database:
  # ...
<% end %>

currently the following works but it's kind of a long and ugly hack (that is actually not supposed to work) : (Java::JavaClass.for_name('org.killbill.billing.osgi.bundles.jruby.JRubyPlugin') rescue false)

some viable alternatives to use :

KILLBILL_VERSION (or KILLBILL_PLATFORM_VERSION or KILLBILL_SERVER_VERSION) constant that would reflect the server's version

dis-advantages - maybe too similar to gem Killbill::VERSION ? (also I'm not sure how to retrieve the version - parsing the pom.properties in jar is an option but I guess OSGi should now that already)
introduce and use ENV['KILLBILL_ENV'] == 'production' - coupling to a single ENV value seems limiting for the future

depends on JRubyPlugin itself as it would need to expose the constant early-on while setting up the JRuby embed container.

... from https://github.com/killbill/killbill-plugin-framework-ruby/issues/37#issuecomment-94719888

killbill / killbill-plugin-framework-ruby

expose a global constant that identifies running inside KB #39