GHSA-JMXC-HHWX-GVV3 Private Lemmy instances expose multi-community metadata without authentication

NOTE: Only affects development version. Summary readmulticommunity does not enforce the private-instance setting. On a private instance, an unauthenticated visitor can read multi-community names, titles, summaries, sidebars, owner identities, and member community lists. Details Other read handler...