GODT-1381: Use in-memory cache in case local cache is unavailable

- change: refactor GUI notification object
- add: global bridge errors
- add: when cache on disk cannot be initialized fallback to memory cache
- add: show notification for CoD failure
- change: do not allow login to IMAP and SMTP when CoD init failed

internal/frontend/types/types.go

@@ -86,6 +86,7 @@ type Bridger interface {
 	SetUpdateChannel(updater.UpdateChannel)
 	GetKeychainApp() string
 	SetKeychainApp(keychain string)
+	HasError(err error) bool
 }
 
 type bridgeWrap struct {