is something like this supposed to work (extending a type in types.graphql):

# model-user (coming from a file somewhere)

type User @model {
  id: ID! @isUnique
  email: String!
}

# model-paper (coming from another file somehwere)

extend type User {
  papers: [Paper!]! @relation(name: "UserPapers")
}

type Paper @model {
  id: ID! @isUnique
  title: String!
  author: User! @relation(name: "UserPapers")
}