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Go to https://oss.sonatype.org/#stagingRepositories and there should be a newly created grouper repository with the artifacts inside. The login and password for Sonatype can be found in ~/.m2/settings.xml.
Maven central is https://search.maven.org/search?q=grouper
If the objects are all there and look ok, click the close icon to freeze the repository. At that point, you should test the objects, by trying to building something, using the staging repository as if it were the release repository. In your .m2/settings.xml, add:
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