Support multiple unique fields in dgraph GraphQL

Hi @jdgamble555, support for multiple @id’s is already added in graphql and available in 21.03. In addition to that we also added some more features to @id fields like mutable and nullable @id fields which will be avaliable in 21.07. follow the below link for more details.
RFC: RFC: Allow multiple unique fields in graphql schema
PR: Feat(GraphQL): This PR allow multiple @id fields in a type. by JatinDevDG · Pull Request #7235 · dgraph-io/dgraph · GitHub