Deploy SNAPSHOTs via GitHub Actions

[kwin]

A valid OSSRH token should be used as repository secret to automatically deploy the main branch to the OSSRH snapshot repository via GitHub Actions.

[cstamas]

Unsure do we want this... it will be always a PITA to maintain... either one of our token will needed (that will expire), but, we are NOT allowed to admin the secrets, so IT gitlab issue is needed, etc...

IMHO, we do not want to deploy snapshots... we (all 3 of us) can always deploy "fresh" snapshot if someone wants to test it (mvn clean deploy -P sisu-release).

In short: this will require "secret" management, we are not allowed to do, hence we will always need to ask for IT support.... and is just not convenient IMO.

[kwin]

I think we need to rely on Eclipse Snapshot repository for providing SNAPSHOTS (instead of OSSRH). Its token is provided by Eclipse INFRA and does not expire (https://github.com/eclipse-cbi/cbi/wiki/Nexus)

[kwin]

I requested an Eclipse Nexus Snapshot repo in https://gitlab.eclipse.org/eclipsefdn/helpdesk/-/issues/5012.