Re-add the CloudSync functionality

It got removed in the marketplace upgrade.

CURA-9146

plugins/Marketplace/CloudSync/DiscrepanciesPresenter.py

@@ -0,0 +1,41 @@
+import os
+from typing import Optional
+
+from PyQt6.QtCore import QObject
+
+from UM.Qt.QtApplication import QtApplication
+from UM.Signal import Signal
+from .SubscribedPackagesModel import SubscribedPackagesModel
+
+
+class DiscrepanciesPresenter(QObject):
+    """Shows a list of packages to be added or removed. The user can select which packages to (un)install. The user's
+
+    choices are emitted on the `packageMutations` Signal.
+    """
+
+    def __init__(self, app: QtApplication) -> None:
+        super().__init__()
+
+        self.packageMutations = Signal()  #  Emits SubscribedPackagesModel
+
+        self._app = app
+        self._package_manager = app.getPackageManager()
+        self._dialog = None  # type: Optional[QObject]
+        self._compatibility_dialog_path = "resources/qml/CompatibilityDialog.qml"
+
+    def present(self, plugin_path: str, model: SubscribedPackagesModel) -> None:
+        path = os.path.join(plugin_path, self._compatibility_dialog_path)
+        self._dialog = self._app.createQmlComponent(path, {"subscribedPackagesModel": model, "handler": self})
+        assert self._dialog
+        self._dialog.accepted.connect(lambda: self._onConfirmClicked(model))
+
+    def _onConfirmClicked(self, model: SubscribedPackagesModel) -> None:
+        # If there are incompatible packages - automatically dismiss them
+        if model.getIncompatiblePackages():
+            self._package_manager.dismissAllIncompatiblePackages(model.getIncompatiblePackages())
+        # For now, all compatible packages presented to the user should be installed.
+        # Later, we might remove items for which the user unselected the package
+        if model.getCompatiblePackages():
+            model.setItems(model.getCompatiblePackages())
+            self.packageMutations.emit(model)