add EnablePreviewModeBanner in config (#8834)

Signed-off-by: Saturnino Abril <saturnino.abril@gmail.com>

model/config.go

@@ -739,6 +739,7 @@ type EmailSettings struct {
 	EnableEmailBatching               *bool
 	EmailBatchingBufferSize           *int
 	EmailBatchingInterval             *int
+	EnablePreviewModeBanner           *bool
 	SkipServerCertificateVerification *bool
 	EmailNotificationContentsType     *string
 	LoginButtonColor                  *string
@@ -791,6 +792,10 @@ func (s *EmailSettings) SetDefaults() {
 		s.EmailBatchingInterval = NewInt(EMAIL_BATCHING_INTERVAL)
 	}
 
+	if s.EnablePreviewModeBanner == nil {
+		s.EnablePreviewModeBanner = NewBool(true)
+	}
+
 	if s.EnableSMTPAuth == nil {
 		s.EnableSMTPAuth = new(bool)
 		if s.ConnectionSecurity == CONN_SECURITY_NONE {