Fix caching of future broadcast messages

What does this MR do?

This fixes caching of broadcast messages so messages set to show up in the future are cached/displayed correctly.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Tests added for this feature/bug
• Review
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together