Old Community portal: Once the new platform is ready, the community portal should be read-only.

Once the new AIoD front-end is up and running, and content is migrated as described in https://github.com/aiondemand/roadmap/issues/33 the community portal will disable the Contribution Gateway https://www.ai4europe.eu/contribute making it impossible to add new content.

A banner should exist that should inform users that contributions are now only accepted via the new url (the new platform)