Feature request

As a Nextcloud user I prefer to use my email program without threads and look at messages separately.

Work packages

• Add a checkbox per Nextcloud account (or Nextcloud Mail account - to be decided) to turn threading off. It's opt-out and, feature will be on by default.
• When threading is enabled do everything like before. Make sure previously not threaded accounts are fully rethreaded if necessary.
• When threading is disabled set thread_root_id=message_id for all messages and skip threading after synchronization
• User documentation

Follow-ups

• Add an admin toggle for user defaults
  • Admin leaves thread on -> threading is on for users unless they disable it
  • Admin opts out -> threading is off for users unless they enable it
  • This will then require admin documentation

Original request