[Guided Setup Stage 2] Update HandleSpecialChatReportsOnMergeAccount to handle system DM

[francoisl]

Part of the "wave-collect – Build Stage 2 of Guided Setup" project

Main issue: https://github.com/Expensify/Expensify/issues/356685
Doc section: https://docs.google.com/document/d/10bhCv6XtzzqEZQ9tzxFwAz4lowgjOhsFqz13BMq6Iu4/edit#heading=h.dmxmb440p80k (and section below)
Project: [#whatsnext] #wave-collect

Feature Description

• Create the concept of read-only messages by updating the permissions mechanism
• Create a read-only system DM using the new Expensify persona for existing and new users

Remaining tasks

• Make Account writing to chat/task report without permission throw
• Handle MergeAccount
  • Update HandleSpecialChatReportsOnMergeAccount to handle system DM
  • Remove HandleSelfDMOnMergeAccount from AuthCommandMap

Upwork Automation - Do Not Edit

• Upwork Job URL: https://www.upwork.com/jobs/~010dca0075d6efe79d
• Upwork Job ID: 1770904803490025472
• Last Price Increase: 2024-03-21

[melvin-bot]

Job added to Upwork: https://www.upwork.com/jobs/~010dca0075d6efe79d

[melvin-bot]

Triggered auto assignment to Contributor Plus for review of internal employee PR - @getusha (Internal)

[melvin-bot]

Triggered auto assignment to @CortneyOfstad (NewFeature), see https://stackoverflowteams.com/c/expensify/questions/14418#:~:text=BugZero%20process%20steps%20for%20feature%20requests for more details.

[melvin-bot]

⚠️ It looks like this issue is labelled as a New Feature but not tied to any GitHub Project. Keep in mind that all new features should be tied to GitHub Projects in order to properly track external CAP software time ⚠️

[francoisl]

This is all backend work and will be taken care of internally, no need for a C+ here.