Transient proxy request errors during external OIDC flow on iOS

[wojcik91]

When authenticating with external OIDC sometimes a following error appears:

This happens inconsistently, we have not yet been able to reproduce it reliably.
This also does not seem to be a timeout error since the timeout is much longer and already has a dedicated error message.

[filipslezaklab]

From what I could find this is related to when iOS loses network for a brief moment, for now I would focus on providing more readable error in this case. @kchudy