gui: add subscription to Step trait

gui/src/installer/mod.rs

@@ -71,7 +71,10 @@ impl Installer {
     }
 
     pub fn subscription(&self) -> Subscription<Message> {
-        Subscription::none()
+        self.steps
+            .get(self.current)
+            .expect("There is always a step")
+            .subscription()
     }
 
     pub fn stop(&mut self) {

gui/src/installer/step/mod.rs

@@ -14,7 +14,7 @@ pub use mnemonic::{BackupMnemonic, RecoverMnemonic};
 
 use std::path::PathBuf;
 
-use iced::Command;
+use iced::{Command, Subscription};
 use liana::miniscript::bitcoin::bip32::Fingerprint;
 
 use liana_ui::widget::*;
@@ -25,6 +25,9 @@ pub trait Step {
     fn update(&mut self, _message: Message) -> Command<Message> {
         Command::none()
     }
+    fn subscription(&self) -> Subscription<Message> {
+        Subscription::none()
+    }
     fn view(&self, progress: (usize, usize)) -> Element<Message>;
     fn load_context(&mut self, _ctx: &Context) {}
     fn load(&self) -> Command<Message> {