RFR: 1628: Restore 'createdAt' in GraphQL queries

[Erik Joelsson]

This patch restores the field name "createdAt" which was mistakenly search-replaced to "at" by my IDE in SKARA-1584. I have verified by manually running against Github.

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Commit messages:
 - SKARA-1628

Changes: https://git.openjdk.org/skara/pull/1392/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1392&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1628
  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/skara/pull/1392.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1392/head:pull/1392

PR: https://git.openjdk.org/skara/pull/1392