Called by:

• Mobilizon.Federation.ActivityPub.Transmogrifier.handle_incoming (L154)
• Mobilizon.Federation.ActivityPub.Transmogrifier.handle_incoming (L631)
• Mobilizon.GraphQL.API.Participations.join (L21)
• Mobilizon.GraphQL.Resolvers.Group.join_group (L301)