Details are needed for more errors the vpn-client app may have

[Senyoret1]

When there is an error that stops the vpn-client app, the API returns a description about the error in the detailed_status field of the vpn-client app when calling /api/visors/{pk}/summary. The problem is that the field does not get a description after some errors, like when the server visor is closed while the client is connected to it.

It would be good to consider all the common problems and make sure the API returns error messages for them.