Dedupe Apollo Client 3 references in merge

dedupeApolloReferences.js

function dedupeReferences (existing, incoming) {
  // Dedupe items
  const idMap = {}
  for (const item of existing) {
    idMap[item.__ref] = true
  }
  const validated = []
  for (const item of incoming) {
    if (!idMap[item.__ref]) {
      validated.push(item)
    }
  }
  return [...existing, ...validated]
}