Create and publish a GPG signature for use by the kessel api java client committers for signing the maven generated artifacts in automations.

See manual steps (at time of writing):

https://docs.google.com/document/d/1MR4l0qUGdXIFraP-3Ke7V0isHTD3I4-FeYGbedUhEWQ/edit?usp=sharing 

See Maven central requirements:

https://central.sonatype.org/publish/requirements/

Requirements:

1. May require a project-kessel.org email address (TBD), since signatures require an email.

Acceptance criteria:

1. Generate a GPG signature representing the kessel java client committers.
2. Publish the GPG signature to a suitable server.
3. Ensure the signature is used in the pipelines in RHCLOUD-33051 and RHCLOUD-33050, and that the private key is stored appropriately.