add dateupdate to the records in the dgraphDB

[sgluege]

Each Record has an updateDate ... add it to the query

type InfoObject @withSubscription { title: String @search(by: [fulltext]) persons: [ Person ] authors: [ Author ] year: Int @search abstract: String @search(by: [fulltext]) language: String link: String! @id @search(by: [exact]) extras: String @search(by: [fulltext]) sdgs: [ Sdg ] @hasInverse(field: objects) keywords: [ Keyword ] class: [ PublicationClass ] category: InfoObjectType @hasInverse(field: objects) subtype: InfoObjectSubType @hasInverse(field: objects) departments: [Department] @hasInverse(field: objects) dateUpdate: DateTime }