improve backend features management for every command

src/account/command/sync.rs

@@ -101,7 +101,7 @@ impl AccountSyncCommand {
         let account_name = account_config.name.as_str();
 
         let backend_builder =
-            BackendBuilder::new(toml_account_config, account_config.clone(), false).await?;
+            BackendBuilder::new(toml_account_config, account_config.clone()).await?;
         let sync_builder = AccountSyncBuilder::new(backend_builder.into())
             .await?
             .with_some_folders_strategy(strategy)

src/account/config.rs

@@ -111,6 +111,14 @@ impl TomlAccountConfig {
             .or_else(|| self.backend.as_ref())
     }
 
+    pub fn watch_envelopes_kind(&self) -> Option<&BackendKind> {
+        self.envelope
+            .as_ref()
+            .and_then(|envelope| envelope.watch.as_ref())
+            .and_then(|watch| watch.backend.as_ref())
+            .or_else(|| self.backend.as_ref())
+    }
+
     pub fn add_flags_kind(&self) -> Option<&BackendKind> {
         self.flag
             .as_ref()