Note that you must be a public member of akka org to trigger builds a…

…kka#22543

CONTRIBUTING.md

@@ -266,6 +266,8 @@ In order to force the `validatePullRequest` task to build the entire project, re
 changes one can use the special `PLS BUILD ALL` command (typed in a comment on GitHub, on the pull request), which will cause
 the validator to test all projects.
 
+Note, that `OK TO TEST` will only be picked up when the user asking for it is considered an admin. Public (!) members of the [akka organization](https://github.com/orgs/akka/people) are automatically considered admins and users manually declared admin in the Jenkins job (currently no one is explicitly listed). `PLS BUILD` and `PLS BUILD ALL` can be issued by everyone that is an admin or everyone who was whitelisted in the Jenkins Job (whitelisting != declaring someone an admin).
+
 ## Source style
 
 ### Scala style