hook backup_is_done

I expect to use this hook in add-on 529955533. It'll serve me to
create long term backup at the same time than your backup

qt/aqt/gui_hooks.py

@@ -272,6 +272,30 @@ class _AvPlayerWillPlayHook:
 av_player_will_play = _AvPlayerWillPlayHook()
 
 
+class _BackupIsDoneHook:
+    _hooks: List[Callable[[], None]] = []
+
+    def append(self, cb: Callable[[], None]) -> None:
+        """()"""
+        self._hooks.append(cb)
+
+    def remove(self, cb: Callable[[], None]) -> None:
+        if cb in self._hooks:
+            self._hooks.remove(cb)
+
+    def __call__(self) -> None:
+        for hook in self._hooks:
+            try:
+                hook()
+            except:
+                # if the hook fails, remove it
+                self._hooks.remove(hook)
+                raise
+
+
+backup_is_done = _BackupIsDoneHook()
+
+
 class _BrowserDidChangeRowHook:
     _hooks: List[Callable[["aqt.browser.Browser"], None]] = []
 

qt/aqt/main.py

@@ -561,6 +561,7 @@ from the profile screen."
             fname = backups.pop(0)
             path = os.path.join(dir, fname)
             os.unlink(path)
+        gui_hooks.backup_is_done()
 
     def maybeOptimize(self) -> None:
         # have two weeks passed?

qt/tools/genhooks_gui.py

@@ -341,6 +341,7 @@ hooks = [
     ),
     # Main
     ###################
+    Hook(name="backup_is_done"),
     Hook(name="profile_did_open", legacy_hook="profileLoaded"),
     Hook(name="profile_will_close", legacy_hook="unloadProfile"),
     Hook(