Add milestones / to-dos for HIFIS Backbone in 2023, aligned with HIFIS + Backbone Cluster Report 2022, pp 26-27.

• Review here (orange milestones in 2023 only)
  • Review App Access credentials (HIFIS internal)
• Edit here (one file per milestone)

• Shorten texts a bit
• Review
• Rebase on master before merge (cloud MS are currently included to have a reference on the overall look)