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/imap/backend.go

@@ -39,6 +39,7 @@ import (
 	"github.com/ProtonMail/proton-bridge/internal/bridge"
 	"github.com/ProtonMail/proton-bridge/internal/config/settings"
 	"github.com/ProtonMail/proton-bridge/internal/events"
+	"github.com/ProtonMail/proton-bridge/internal/users"
 	"github.com/ProtonMail/proton-bridge/pkg/listener"
 	"github.com/emersion/go-imap"
 	goIMAPBackend "github.com/emersion/go-imap/backend"
@@ -168,6 +169,10 @@ func (ib *imapBackend) Login(_ *imap.ConnInfo, username, password string) (goIMA
 	// Called from go-imap in goroutines - we need to handle panics for each function.
 	defer ib.panicHandler.HandlePanic()
 
+	if ib.bridge.HasError(bridge.ErrLocalCacheUnavailable) {
+		return nil, users.ErrLoggedOutUser
+	}
+
 	imapUser, err := ib.getUser(username)
 	if err != nil {
 		log.WithError(err).Warn("Cannot get user")

internal/imap/bridge.go

@@ -30,6 +30,7 @@ type cacheProvider interface {
 
 type bridger interface {
 	GetUser(query string) (bridgeUser, error)
+	HasError(err error) bool
 }
 
 type bridgeUser interface {