User roles for writing news, adding highlights and others

[cmeessen]

News items, new software highlights, announcements etc. can currently only be maintained by administrators. This means, if tasks are distributed to multiple people, they must become administrators of the RSD instance. In terms of data protection, this is not ideal, especially since this also allows users to have full write access to any software, project or e.g. the Terms of Service. It would be good if roles could be assigned to individual users, where each role allows the user to maintain individual aspects of the RSD.

For the beginning, the roles could include:

• News editor (write, read unpublished and publish news)
• Software highlights maintainer (add/remove highlights to/from the list)
• Organisation admin (full access to all organisations)
• Projects admin (full access to all projects)

Related: #647