chore(GODT-2799): Separate account states for SMTP Backend

Rather than accessing the Bridge user list, each user register their
individual SMTP service with the server manager.

Note that some dependencies on the user data are hidden behind the
`UserInterface`. These will be removed in a future patch.

internal/services/smtp/service.go

@@ -19,6 +19,7 @@ package smtp
 
 import (
 	"context"
+	"errors"
 	"io"
 
 	"github.com/ProtonMail/gluon/async"
@@ -34,7 +35,10 @@ import (
 // UserInterface is just wrapper to avoid recursive go module imports. To be removed when the identity service is ready.
 type UserInterface interface {
 	ID() string
+	CheckAuth(string, []byte) (string, error)
 	WithSMTPData(context.Context, func(context.Context, map[string]proton.Address, proton.User, *vault.User) error) error
+	ReportSMTPAuthSuccess(context.Context)
+	ReportSMTPAuthFailed(username string)
 }
 
 type Service struct {
@@ -91,6 +95,10 @@ func (s *Service) Start(group *async.Group) {
 	})
 }
 
+func (s *Service) UserID() string {
+	return s.user.ID()
+}
+
 func (s *Service) run(ctx context.Context) {
 	s.log.Debug("Starting service main loop")
 	defer s.log.Debug("Exiting service main loop")
@@ -128,5 +136,13 @@ type sendMailReq struct {
 
 func (s *Service) sendMail(ctx context.Context, req *sendMailReq) error {
 	defer async.HandlePanic(s.panicHandler)
-	return s.smtpSendMail(ctx, req.authID, req.from, req.to, req.r)
+	if err := s.smtpSendMail(ctx, req.authID, req.from, req.to, req.r); err != nil {
+		if apiErr := new(proton.APIError); errors.As(err, &apiErr) {
+			s.log.WithError(apiErr).WithField("Details", apiErr.DetailsToString()).Error("failed to send message")
+		}
+
+		return err
+	}
+
+	return nil
 }