## Context
There is no calendarChannel syncStatus column compared to the
messageChannel table. In the meantime, we are trying to infer its status
based on the fact that the connection hasn't failed and the sync is
enabled
- If sync fails we set authFailedAt
- This information is displayed in the frontend in accounts with a `Sync
Failed` pill
- The user can reconnect his account in the dropdown menu
- A new OAuth flow is triggered
- The account is synced
