Show "Action Neeed" error banner when CalDAV connection is broken

[davinotdavid]

Is your feature request related to a problem? Please describe.
Currently, we show an error banner when there's a problem with a connected Google account that also have a default calendar in it. This is how it shows up:

Also, this is currently triggered by raising an exception with a specific id GOOGLE_REFRESH_ERROR.

Describe the solution you'd like
It would be nice to either have the same behaviour for CalDAV or remove this banner logic altogether. Probably this needs to be talked through with the Design team!

To make this happen we should also consider multiple external connection problems from different providers. Do we show one banner for each connection (as in, if someone has a broken Google, CalDAV and Zoom connection, do we show 3 banners)?

Additional context
#1509 (review)

[MelissaAutumn]

For context: This was a quick fix for our Google refresh tokens expiring every 7 days. That particular issue has been fixed since we verified out Google App (was ages ago now.)

[davinotdavid]

@MelissaAutumn Thanks for the context! It seems that we are leaning towards removing the banner altogether since Design have other patterns, even though it was a happy accident to show it during the external connection issues work.