Will go through Test Plan a couple times in my environment.
1. Patch in this diff
2. Rebase and "stop on" (edit) "DUMMY` commit
3. Run `yarn dev` everywhere and observe the `ThreadInfo`s via Redux DevTools. Observe that there are member permissions for thin threads.
4. `git rebase --continue`
5. Observe the logs in browser dev tools and confirm that migration ran successfully
6. Observe that thin threads no longer have member permissions via Redux DevTools.
---
Before (thin, with member permissions):
{F2926333}
Before (thick, with member permissions):
{F2926335}
---
After (thin, WITHOUT member permissions):
{F2926336}
After (thick, still WITH member permissions):
{F2926371}